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The  American 
Steel  Worker 


CO 


A    TWENTY-FIVE    YEARS'    EXPERIENCE    IN    THE    SELECTION, 
ANNEALING,  WORKING,  HARDENING  AND  TEM- 
PERING OF  VARIOUS  KINDS  AND 
GRADES  OF  STEEL 


<L<?==5L   /=^>9 


CO 

BY 

E.  R.  Markham 


CO 


First  Edition 
1903 


New  York 


II  fi  n  LIRRARr 


Copyright  1903  by  E.   R.   Markham, 


Words  are  not  adequate  to  express  the  debt 
I  owe  one,  who,  more  than  all  others,  has  been 
instrumental  in  instructing,  advising  and  assisting 
me  along  lines  that  have  led  to  whatever  success 
I  may  have  attained. 

As  an  humble  acknowledgement  of  my  grat- 
itude, I  dedicate  this  work 

To  My  Father, 

RUSSELL  MARKHAM. 


The  American 
Steel  Worker. 


Q^<^=\  ,^=^n9 


CO 

Introduction. 

An  experience  which  covers  twenty-five  years  of 
actual  practice,  in  the  various  branches  of  machine 
shop  work,  has  taught  the  writer  that  much  more 
depends  on  the  condition  of  the  various  cutting  tools 
used,  than  mechanics  in  general  realize. 

The  various  machines  used  in  working  iron  and 
steel  to  shape  have  been  improved,  and  made  heavier 
in  the  parts  subjected  to  strain,  in  order  that  heavier 
cuts  and  faster  feeds  might  be  taken  to  reduce  the  cost 
of  production. 

If  a  tool  is  doing  the  maximum  amount  of  work 
possible  for  it  to  do,  when  it  is  used  in  a  light  machine, 
it  would  be  folly  to  purchase  a  heavier,  stronger  ma- 
chine and  use  the  same  tool  in  it.  But  it  has  been 
found  in  many  cases  that  cutting  tools  could  be  made 
that  would  take  heavier  cuts  and  faster  feeds  than  the 
older  types  of  machines  could  carry.  Consequently  it 
has  been  necessary  to  re-design  most  types  of  machines 
iised  to  remove  stock,  in  order  to  bring  them  into 
shape  to  be  used  as  tools,  parts  of  machines,  and  other 
apparatus. 

Competition  has  made  it  absolutely  necessary  that 
every  possible  means  be  taken  to  reduce  the  cost  of  an 


Cheapening  cost  of  production. 

article  without  reducing  the  quality.  Where  possible 
the  design  is  changed  so  the  article  may  be  made  more 
cheaply.  And  as  labor  is,  generally  speaking,  the  princi- 
pal factor  to  be  considered,  it  is  necessary  to  reduce  as 
far  as  possible  the  number  of  operations,  or  simplify 
those  necessary,  and  so  reduce  the  cost  of  the  manu- 
factured article. 

If  by  the  use  of  machinery  especially  adapted  to 
the  work  to  be  done,  it  is  possible  to  do  in  one  opera- 
tion the  work  which  formerly  required  four  separate 
operations,  then  the  amount  paid  for  labor  has  been 
very  materially  reduced,  without  necessarily  reducing 
the  pay  of  the  operator.  In  fact  it  is  found  possible  in 
many  cases  to  increase  his  compensation,  and  at  the 
same  time  reduce  the  cost  per  piece  of  work  very 
materially. 

Now,  in  order  that  improved  machinery  may  do  its 
maximum  amount  of  work  per  day,  it  is  necessary  to 
have  the  cutting  tools,  fixtures,  etc.,  made  in  a  manner 
that  allows  them  to  do  their  part  of  the  work.  If  a 
milling  machine  were  bought  and  set  up  in  a  shop,  and 
it  was  found  that  the  fixtures  formerly  used  in  holding 
the  pieces  of  work  were  not  strong  enough  to  hold 
them  when  the  new  machine  was  taking  the  heaviest 
cut  possible,  heavier  fixtures  would  be  made  at  once  in 
order  that  the  investment  of  money  made  in  purchas- 
ing the  machine  might  not  be  considered  as  having 
been  thrown  away.  Following  out  the  same  line  of 
reasoning,  it  would  be  necessary  to  make  cutting  tools 
of  a  design  that  made  it  possible  to  take  as  heavy  cuts, 
and  use  as  coarse  feeds,  as  the  strength  of  the  machine 
and  fixtures  would  allow. 

While  manufacturers  in  general  recognize  the  im- 

8 


Waste  through  improper  handling. 

portance  of  having  machines  especially  fitted  for  their 
needs,  many  times  the  good  work  stops  right  at  this 
point.  They  are  not  educated  to  a  point  that  makes 
it  possible  for  them  to  comprehend  the  importance  of 
having  the  cutting  tools  hardened  in  a  manner  that 
insures  their  doing  the  amount  of  work  possible. 

While  it  is  often  necessary  to  re-design  cutting 
tools  to  get  added  strength,  many  times  this  needed 
strength  may  be  had  by  proper  hardening. 

A  manufacturer  of  a  high  grade  tool  steel,  in  con- 
versation with  the  writer,  said,  if  he  could  have  one  per 
cent,  of  the  value  of  steel  in  this  country  spoiled  by 
improper  hardening,  he  would  not  exchange  his  income 
for  that  of  the  President  of  the  United  States.  By  the 
value  of  steel,  he  meant  its  value  at  the  time  the  article 
was  hardened.  A  piece  of  steel  which  cost  fifty  cents 
in  the  bar,  may  be  worth  many  dollars  when  ready  for 
hardening,  and  represents  to  the  manufacturer  the 
total  cost  of  steel  and  labor. 

This  line  of  reasoning  might  be  carried  a  great 
deal  further.  If  a  tool  which  is  made  to  do  a  certain 
job  is  ruined,  the  time  the  machine  or  machines  stand 
idle  waiting  for  another  one  to  be  made,  many  times 
represents  a  greater  loss  than  the  money  value  of  the 
tool.  This  is  especially  true  where  the  time  given  to 
complete  the  job  is  limited. 

If  a  tool  is  hardened  in  a  manner  that  makes  it 
impossible  for  it  to  do  as  much  or  as  good  work  as  it 
ought,  the  loss  may  be  greater  than  in  either  of  the 
cases  before  cited,  yet  this  loss  is  seldom  taken  into 
consideration. 

The  writer's  experience  has  convinced  him  that 
few  mechanics  realize  the  vast  waste  of  time  in  many 


Increase  of  productive  efficiency. 

shops,  because  tools  are  not  capable  of  doing  the  amount 
of  work  possible  were  they  properly  hardened.  Take 
for  instance  a  milling  machine  cutter  which  runs  at  a 
periphery  speed  of  thirty-six  feet  per  minute,  milling  a 
mild  grade  of  machinery  steel.  It  is  found  necessary 
to  stop  this  machine  once  in  twenty  working  hours  to 
sharpen  the  cutter,  milling  in  the  meantime  five  hun- 
dred pieces.  A  cutter  is  made  from  the  same  bar,  and 
hardened  by  a  process  that  makes  it  possible  to  run  the 
tool  at  a  periphery  speed  of  eighty  feet  per  minute,  and 
it  is  then  found  necessary  to  grind  but  once  in  two  hun- 
dred hours;  milling  in  the  meantime  eight  thousand 
pieces.  Not  only  is  the  efficiency  of  this  machine 
increased  many  fold,  but  the  expense  of  grinding,  and 
the  necessary  delay  incident  to  stopping  the  machine, 
changing  cutters  and  setting  up,  and  the  cost  of  tools 
per  piece,  is  reduced  very  appreciably. 

Does  some  one  ask.  How  is  this  trouble  to  be 
remedied?  The  answer  is,  men  must  be  educated  to 
see  the  enormous  waste  going  on  all  the  time;  the 
waste  of  steel,  of  time  required  to  make  the  tools,  of 
the  time  valuable  equipment  is  laying  idle,  and  the 
small  percentage  of  work  produced  per  machine,  all  go 
to  reduce  dividends,  and  this  because  so  little  attention 
is  given  a  subject  which  should  receive  as  much  con- 
sideration as  any  one  branch  of  machine  shop  work. 

When  the  trouble  is  apparent,  then  it  is  necessary 
to  find  a  remedy.  The  physician  must  necessarily  un- 
derstand the  human  body  in  order  that  he  may  diagnose 
diseases.  If  one  would  be  a  successful  hardener  of 
steel,  he  must  understand  the  nature  and  peculiarities 
of  steel.  As  a  study  of  drugs  alone  would  not  fit  one 
to  practice  medicine,  neither  will  practice  alone  fit  one 


Necessity  for  the  study  of  steel. 

to  harden  steel,  especially  if  new  problems  are  con- 
stantly coming  up. 

At  the  present  time  when  libraries  are  accessible 
to  nearly  every  one,  and  books  and  mechanical  journals, 
treating  on  steel  and  the  proper  methods  of  its  manipu- 
lation, are  within  the  reach  of  all,  there  is  no  good 
reason  why  ignorance  of  a  subject  so  interesting,  and 
at  the  same  time  of  such  vital  importance  to  both 
manufacturer  and  mechanic,  should  be  so  general. 

A  study  of  the  nature  of  steel  will  convince  one  of 
the  importance  of  extreme  carefulness  when  heating 
either  for  forging,  annealing  or  hardening.  A  man 
who  understands  the  effect  of  heat  on  high  carbon  tool 
steel  is  often  amazed  at  the  careless  manner  which 
many  old  blacksmiths  assume  when  heating  a  piece  of 
steel.  A  difference  of  loo  to  200  degrees  of  heat  after 
the  steel  is  red  hot,  does  not,  according  to  their  idea, 
injure  the  steel  in  the  least,  but  in  reality  it  makes  a 
vast  amount  of  difference  in  the  strength  of  the  piece. 

In  some  shops  a  man  is  called  a  successful  hard- 
ener if  he  is  fortunate  enough  to  avoid  cracking  the 
pieces  he  is  called  upon  to  harden.  Apparently  no 
account  is  taken  of  the  capability  of  the  tool  to  perform 
a  satisfactory  amount  of  work.  A  man  who  devotes 
his  attention  to  hardening  steel  in  a  manner  to  avoid 
cracking,  regardless  of  the  utility  of  the  tool,  is  not 
worthy  of  the  title  of  a  successful  hardener ;  he  should 
be  styled,  as  an  eminent  mechanic  calls  this  class, 
a  non-cracker.  Now,  it  is  possible  to  harden  steel  in  a 
manner  that  does  away  with  the  liability  of  cracking, 
yet  gives  it  the  amount  of  hardness  necessary,  in  order 
that  it  may  do  the  amount  of  work  expected  of  it. 

A  study  of  the  effects  of  expansion  and  contraction 

II 


Expansive  properties  of  steel. 

of  steel  in  the  fire  and  baths  is  necessary  in  order  to 
select  the  proper  forms  of  furnaces  and  bath,  so  that 
the  best  results  may  be  obtained.  Suppose  a  micro- 
meter is  left  for  some  time  in  a  room  where  the  tem- 
perature is  40  degrees  Fahr. ,  a  piece  of  work  is  placed 
between  the  contact   surfaces,   as   shown  in   Fig.    i. 


Figure  1 


Illustrating  expansion  of  steel. 

Now  grasp  the  micrometer  by  the  frame  at  the  portion 
marked  by  with  a  warm  hand;  in  a  few  seconds  the 
metal  will  have  expanded  to  a  degree  that  allows  the 
work  a  to  drop  from  the  gauge,  thus  proving  that  but 
a  very  small  amount  of  heat  is  needed  to  expand  the 
steel  sufficiently  so  the  contact  points  no  longer  touch 
the  piece  between  them. 

Now,  if  a  few  degrees  of  heat  will  expand  steel  so 
it  can  be  readily  observed,  it  is  apparent  that  a  heat  of 
900  to  1,200  degrees  Fahr.  must  cause  the  process  of 
expansion  to  be  carried  to  a  much  greater  extent.  The 
amount  of  heat  necessary  to  give  steel,  in  order  that  it 
may  harden  when  plunged  in  some  cooling  bath,  varies 
with  the  make  of  steel,  the  percentage  of  carbon  it  con- 


Desirability  of  not  overheating. 

tains,  and  also  on  the  percentage  of  other  hardening 
elements  in  the  steel.  Jarolinech  places  the  critical 
temperature  at  932  degrees  Fahr.  (500  Centigrade)  as 
determined  by  him  experimentally.  The  lowest  heat 
at  which  a  piece  of  steel  will  harden  satisfactorily  is 
termed  the  refining  heat,  because  the  effect  of  the 
operation  of  suddenly  cooling  steel  heated  to  this  tem- 
perature is  to  refine  the  grain,  making  it  the  finest  pos- 
sible. 

The  writer  does  not  propose  giving  a  scientific 
explanation  of  the  changes  which  take  place  in  a  piece 
of  steel  when  it  is  heated  to  the  hardening  heat,  and 
quenched  in  the  cooling  bath,  but  the  practical  sides  of 
the  question  will  receive  careful  attention. 

Every  man  and  boy  working  in  a  machine  shop 
knows  that  steel  heated  red  hot  and  plunged  in  water, 
will  harden,  but  it  is  necessary  to  know  how  hot  it 
must  be  heated  in  order  that  satisfactory  results  may 
follow.  We  should  thoroughly  understand  the  action 
of  too  great  an  amount  of  heat  on  the  structure  of  steel, 
in  order  that  overheating  may  be  avoided.  It  is  also 
necessary  to  have  a  correct  understanding  of  the  effects 
of  baths  of  various  kinds  on  steel,  if  it  is  dipped  in 
them  when  red  hot. 

It  is  an  acknowledged  fact  that  the  lowest  possible 
heat  at  which  steel  will  harden,  leaves  it  the  strongest 
This  is  illustrated  elsewhere.  Knowing  this,  it  will  be 
seen  that  an  article  made  of  steel  is  very  much  less 
liable  to  crack  when  hardened  at  a  low  heat,  than  if  it 
were  heated  to  a  temperature  which  caused  it  to  be 
brittle. 

Commencing  with  cold  steel,  every  degree  of  heat 
applied  changes  in  a  measure  the  size  and  structure 

13 


Uniform  expansion  in  heating. 

of  the  piece,  until  a  certain  limit  is  reached.  Now,  if  a 
change  in  temperature  of  a  few  degrees  changes  the 
size  of  a  piece  of  steel,  the  reader  is  asked  to  imagine 
the  change  in  size  and  structure  which  must  take  place 
when  it  is  heated  red  hot.  This  means  a  change  in 
temperature  of  about  i,ooo  degrees,  and  the  effect  of 
heat  on  steel  is  to  expand  it,  while  the  opposite  effect 
is  accomplished  when  it  is  cooled.  The  more  rapidly 
it  is  cooled  the  harder  it  will  be.  It  is  indeed  wonder- 
ful that  a  piece  of  steel  can  undergo  the  changes  which 
take  place  in  its  size  and  structure,  and  remain  intact. 
When  steel  is  cooled  in  the  hardening  bath,  the  outside 
of  course  chills  and  hardens  first,  while  the  inside  is 
hot  and  consequently  soft  for  some  little  time  after- 
ward. Now,  the  outside,  being  hardened,  is  practically 
inflexible,  while  the  inside  continues  to  change  in 
structure  until  cold.  This  is  especially  true  of  pieces 
having  teeth  or  projections  on  their  surface. 

Understanding  the  fact  that  heat  causes  steel  to 
expand,  it  will  readily  be  seen  that  it  is  absolutely 
necessary  that  it  should  expand  uniformly  throughout 
the  piece.  If  the  corners  and  edges  are  hotter  than  the 
balance  of  the  piece,  then  it  is  unevenly  expanded,  and 
consequently  will  contract  unevenly.  Now,  if  one  part 
of  a  piece  of  steel  contracts  more  than  another,  or  not 
uniformly  with  another  part,  it  is  liable  to  crack  from 
the  effects  of  the  unequal  contraction;  if  it  is  not 
cracked  when  taken  from  the  hardening  bath,  it  is  liable 
to  crack  at  some  future  time  for  no  apparent  reason. 
This  applies  especially  to  large  pieces,  and  steel  having 
a  high  percentage  of  carbon. 


14 


The  Workman 


CO 


The  writer's  professional  experience  in  the  various 
methods  of  working"  steel,  brings  him  in  contact  with 
men  of  all  degrees  of  intelligence.  Some  men  are 
really  skillful  in  the  particular  line  they  are  engaged 
in;  that  is,  they  are  very  careful  when  heating  and 
dipping  in  the  bath,  and  get  excellent  results.  But 
they  do  not  know  the  difference  between  a  steel  of  ^ 
per  cent,  carbon  and  one  of  i  ^  per  cent ;  in  fact,  they 
do  not  know  anything  about  percentages  of  carbon, 
and  don't  care ;  they  say  so  in  as  many  words.  The 
steel  they  use  is  always  the  same  make  and  temper. 
They  have  never  used  anything  else.  If  they  should 
get  hold  of  another  make,  that  worked  differently 
from  that  they  had  always  used,  they  would  condemn 
it,  saying  it  was  no  good,  because  it  didn't  act  just  like 
the  steel  they  were  accustomed  to  handling. 

Now,  if  anything  should  happen  to  the  steel  mill 
making  their  particular  brand,  they  would  be  obliged 
to  learn  the  art  of  hardening  all  over  again,  or  go  out 
of  business.  When  it  becomes  necessary,  or  the  con- 
cern who  employs  these  men  considers  it  advisable, 
to  change  the  steel  used;  or  if  it  is  necessary  to 
have  the  composition  changed  to  get  some  desired  re- 
sult, this  poor  fellow  is  all  at  sea.     He  doesn't  know 

15 


The  workman  who  "knows  it  all." 

what  to  do,  and  he  doesn't  want  anyone  to  tell  him 
what  to  do.  His  only  cry  is,  *'  The  steel  isn't  good  for 
anything,"  when  in  reality  it  may  be  the  best  on  the 
market.  Such  a  man  is  to  be  pitied,  but  he  is  a  very 
expensive  man  for  those  in  whose  employ  he  happens 
to  be,  and  a  very  unpleasant  fellow  to  attempt  to  teach 
anything. 

Another  example  is  the  man  who  banks  on  his 
twenty  or  fifty  years'  experience,  and  considers  that 
because  he  has  been  allowed  to  exist  for  that  length 
of  time  and  occupy  a  position  as  blacksmith,  or 
hardener,  that  he  must  necessarily  know  it  all.  To 
him  steel  is  steel;  he  treats  it  all  alike.  If  there  is 
some  particular  steel  good-natured  enough  to  stand  his 
treatment,  that  is  the  only  brand  on  the  market  fit  to 
use — according  to  his  way  of  thinking — and  he  gener- 
ally has  such  an  unpleasant  and  forcible  personality, 
that  he  either  has  his  say  or  goes  where  he  can.  He 
never  investigates  the  merits  of  different  makes  of 
steel ;  simply  condemns  every  make  that  will  not  stand 
his  abuse. 

If  every  man  of  the  type  under  consideration  ad- 
vocated using  the  same  steel,  there  might  be  a  plausi- 
ble excuse  for  looking  into  the  merits  of  that  particular 
brand,  to  the  exclusion  of  every  other,  but  you  will 
hardly  find  two  of  them  advocating  the  use  of  the  same 
steel.  I  am  happy  to  say  this  class  of  hardener  is  not 
in  as  great  a  majority  as  formerly;  their  number  is 
gradually  diminishing.  It  is  impossible  to  teach  him 
anything,  because  that  long  experience  of  his  stands  in 
the  way ;  it  is  his  only  stock  in  trade,  and  he  presents 
it  every  time  anything  is  said  on  the  subject. 

Now,  a  long  experience  in  any  particular  line  of 
i6 


The  workman  who  doesn*t  care. 

work  is  a  good  thing  for  a  man,  provided  it  has  been  a 
real  experience,  rather  than  an  existence,  and  in  no  line 
of  business  is  it  more  valuable  than  in  the  working  of 
steel,  if  the  man  has  kept  pace  with  the  procession. 
If  not,  then  he  is  no  farther  advanced  than  when 
he  fell  out  of  line,  and  as  it  is  a  law  governing  all  our 
lives,  that  no  man  stands  still,  he  must  of  necessity 
either  advance  or  go  backward.  The  man  who  has  not 
kept  pace  with  the  progress  of  events,  must  necessarily 
go  backwards. 

Another  class  we  meet  with  is  the  jolly,  good- 
natured  fellow,  who  wants  to  please  everybody,  but 
does  not  know  how,  and  is  too  lazy  to  find  out.  He  had 
rather  tell  a  story  than  to  keep  his  eyes  and  attention 
on  the  piece  he  is  heating,  consequently  he  has  all 
kinds  of  luck.  There  is  no  remedy  known  for  this 
chap.  He  is  willing  to  be  told  how  to  do,  but  is  too 
lazy  to  assimilate  and  put  in  practice  what  is  told  him. 

A  class  of  hardeners  which  are  few  in  numbers, 
but  who  should  get  into  some  other  business  as  soon 
as  possible,  consists  of  men  who  are  practically  color 
blind.  They  cannot  distinguish  between  the  various 
shades  of  red,  neither  can  they  discern  the  temper 
colors  as  closely  as  they  should.  Some  of  them  are 
extremely  intelligent,  capable  men,  but  they  have 
missed  their  calling,  and  missed  it  most  decidedly, 
because  a  man  to  be  a  successful  blacksmith  or  hard- 
ener, must  have  good  powers  of  distinguishing  colors 
and  shades. 

There  are  many  other  classes  that  might  be  con- 
sidered, but  it  would  be  a  waste  of  time,  so  we  will 
look  in  upon  the  successful  hardener.  There  are  vari- 
ous degrees  of  success,  but  we  will  consider  the  man 

17 


The  successful  steel  worker. 

who  is  a  success  according  to  the  generally  accepted 
idea. 

The  successful  hardener  is  one  who  finds  out  what 
is  wanted  or  expected  of  the  article  he  is  to  harden; 
whether  extreme  hardness,  toughness  or  elasticity,  or  a 
combination  of  two  of  these  qualities.  He  also  under- 
stands the  nature  and  pecularities  of  the  steel  he  is 
using ;  he  considers  the  fire  he  is  to  use,  and  the  bath 
in  which  the  steel  is  to  be  quenched  after  it  is  heated. 

His  spare  moments  are  not  spent  hanging  around 
street  corners,  or  saloons,  but  in  reading  and  studying 
such  books  and  mechanical  journals  as  treat  on  subjects 
in  his  line.  In  this  way  he  becomes  familiar  with  the 
nature  of  steel  and  knows  what  to  do  when  certain 
conditions  which  are  out  of  the  ordinary  arise ;  he  gets 
the  experience  of  others  and  his  knowledge  makes  it 
possible  for  him  to  discriminate  between  that  which 
will  be  of  value  to  him,  and  that  which  will  not. 

When  a  piece  of  work  is  given  him  he  studies  the 
shape  of  the  piece,  the  best  method  of  heating  and 
quenching,  in  order  to  get  the  desired  results.  To  him 
steel  is  not  simply  steel,  which  must  be  treated  just 
like  every  other  piece  of  the  same  metal,  but  it  is  a 
valuable  tool  or  piece  of  machinery  which  he  takes 
pride  in  hardening  in  the  best  possible  manner.  If  he 
hears  of  a  brand  that  is  giving  some  one  trouble,  he  is 
anxious  to  get  a  piece  of  it,  and  experiment  and  find 
out  why  they  can  not  get  good  results  from  it. 

If  he  hears  of  a  brand  that  some  one  claims  gives 
extra  good  results  when  using,  he  is  anxious  to  get  a 
sample  and  test  it,  and  see  for  himself  if  the  steel  is 
all  the  makers  claim  it  is. 

He  is  not  above  learning,  takes  advantage  of  every 

i8 


The  two  kinds  of  steel. 

opportunity  to  get  the  ideas  and  experience  of  others, 
especially  men  who  have  had  a  wide  experience.  To 
him  the  articles  he  is  called  on  to  harden  represent  so 
much  money  entrusted  to  his  care,  and  he  takes  every 
means  possible  to  get  it  out  in  a  satisfactory  manner. 

Does  some  one  ask,  where  do  you  meet  such  men? 
The  writer  is  happy  to  say  such  men  are  not  the  ex- 
ception. To  be  sure  they  are  not  in  the  majority,  but 
the  number  of  men  who  are  making  a  careful  study  of 
this  subject  is  really  encouraging. 


Steel. 


CO 


Although  there  are  many  makes  of  steel  and,  in 
most  cases,  several  grades  of  the  same  make,  yet  to  the 
average  mechanic  there  are  two  kinds  of  steel,  viz., 
machinery  steel  and  tool  steel. 

Machinery  steel  is  used  in  making  such  parts  of 
machines,  apparatus  or  tools  as  do  not  require  harden- 
ing in  order  to  accomplish  the  result  for  which  they 
are  intended.  Or,  if  they  require  hardening  at  all,  it  is 
simply  a  surface  hardening,  the  interior  of  the  piece 
being  soft  with  a  view  to  obtaining  greater  strength. 
This  class  of  steel  is  of  a  lower  grade  than  tool  steel. 
It  is  softer,  works  more  easily,  both  in  the  operations 
of  forging  and  machining,  and  can  be  safely  heated  to 
a  higher  temperature  without  harm  to  the  steel.     It 


19 


Tool  steel — what  it  is ;  what  it's  for. 

resembles  more  closely  wrought  iron  and  is  sometimes 
scarcely  to  be  distinguished  from  it.  Machinery  steel 
is  used  whenever  it  will  answer  the  purpose,  not  only 
on  account  of  its  being  more  easily  machined,  but  its 
first  cost  is  only  ^  to  -j^  that  of  ordinary  tool  steel, 
and  for  most  purposes  where  it  is  used,  it  answers  the 
purpose  as  well  or  better. 

Although  it  is  considered  advisable  to  group  steel 
under  two  heads,  as  mentioned,  namely,  machinery 
steel  and  tool  steel,  yet  on  account  of  the  different 
grades  of  the  article  under  each  head  it  will  be  neces- 
sary to  distinguish  them  somewhat  as  they  are  con- 
sidered under  the  various  processes  of  hardening. 

Tool  steel  is  made  with  the  idea  in  view  that  it  is 
to  be  made  into  such  tools,  appliances  or  parts  of 
machines  as  require  hardening  in  order  to  accomplish 
the  desired  result.  Although  the  term  "tool  steel" 
is  applied  to  steel  intended  to  be  made  into  cutting 
tools,  there  are  many  makes  of  this  article,  each  make 
differing  in  some  respects  from  every  other  make.  Not 
only  is  this  so,  but  most  makers  put  out  tool  steel  of 
different  tempers.  Now,  the  word  "temper,"  as  used 
by  steel  makers,  means  the  quantity  or  percentage  of 
carbon  the  steel  contains.  It  is  low  temper,  medium, 
or  high,  or  number  or  letter  so  and  so,  according 
to  the  understanding  of  the  marks  in  each  particular 
mill.  The  following  are  considered  by  steel  makers  as 
the  most  useful  tempers  of  tool  steel : 

Razor  temper  (i^  per  cent,  carbon).  This  steel 
is  so  easily  burnt  by  being  overheated  that  it  can  only 
be  placed  in  the  hands  of  very  skillful  workmen. 
When  properly  treated  it  will  do  many  times  the  work 
of  ordinary  tool  steel  when  working  hard  metals,  etc. 


Percentages  of  carbon  in  tool  steel. 

Saw  file  temper  (i|^  per  cent,  carbon).  This  steel 
requires  careful  treatment,  and  although  it  will  stand 
more  heat  than  steel  of  i  ^  per  cent,  carbon,  it  should 
not  be  heated  hotter  than  a  low  red. 

Tool  temper  (i  ^  per  cent,  carbon),  A  very  useful 
temper  for  turning  tools,  drills  and  planer  tools  in  the 
hands  of  ordinary  workmen. 

Spindle  temper  {i}i  per  cent,  carbon).  A  very 
useful  temper  for  mill  picks,  circular  cutters,  very 
large  turning  tools,  screw  thread  dies,  etc. 

Chisel  temper  (i  per  cent,  carbon).  An  exceed- 
ingly useful  temper,  combining,  as  it  does,  great 
toughness  in  the  unhardened  state,  with  a  capacity  of 
hardening  at  a  low  heat.  It  is  well  adapted  for  tools 
where  the  head  or  unhardened  end  is  required  to  stand 
the  blow  of  a  hammer  without  snipping  off,  and  where 
a  hard  cutting  edge  is  required,  such  as  cold  chisels,  etc. 

Set  temper  (^  per  cent,  carbon).  This  temper  is 
adapted  for  tools  where  the  surface  only  is  required  to 
be  hard,  and  where  the  capacity  to  withstand  great 
pressure  is  of  importance,  such  as  stamping  or  pressing 
dies,  etc. 

The  following  also  gives  the  steel  maker's  mean- 
ing of  the  word  ''temper  "  : 

Very  hard 150  carbon  -f 

Hard loo — 120  carbon 

Medium 70 — 80  carbon 

In  order  that  the  reader  may  understand  some- 
thing of  the  significance  of  the  terms  used  to  designate 
the  amount  of  carbon  a  piece  of  steel  contains,  the  fol- 
lowing brief  explanation  is  given.  A  point  is  one 
hundreth  of  one  per  cent,  of  any  element.  100  points 
is  one  per  cent.     A  40  point  carbon  steel  contains  forty 

21 


Peculiarities  of  tool  steel. 

one-hundreths  (.40)  of  one  per  cent,  of  carbon.  The 
same  explanation  applies  to  any  element  that  goes  into 
the  composition  of  steel.  The  steel  is  sometimes  desig- 
nated by  the  number  of  points  of  carbon  it  contains — 
as  20  carbon  or  60  carbon  steel.  The  amount  of  carbon 
the  steel  contains  does  not  necessarily  determine  the 
quality  of  the  steel,  as  the  steel  maker  can  give  an 
ordinary  low  grade  stock  a  very  high  percentage  of 
carbon.  This  would  harden  under  the  ordinary  condi- 
tions, but  would  be  practically  useless  if  made  into 
cutting  or  similar  tools. 

It  becomes  necessary  many  times  to  procure  a  low 
grade  steel  having  as  low  a  percentage  of  carbon  as 
possible.  Then  again  it  is  advisable,  where  a  greater 
amount  of  strength  is  required,  to  give  the  steel  a 
higher  percentage  of  carbon.  This  will  be  briefly 
alluded  to  from  time  to  time  under  the  various  topics. 

The  reader  will  readily  see  from  the  foregoing  that 
it  is  the  presence  of  carbon  in  steel  that  causes  it  to 
harden.  The  amount  of  hardness  and  the  degree  of 
heat  necessary  when  hardening  depending  on  the 
quantity  of  carbon  the  steel  contains.  Tool  steel  is 
hardened  by  heating  it  red  hot  and  plunging  into  some 
coeling  bath.  The  more  quickly  the  heat  is  extracted 
the  harder  the  piece  will  be. 

Tool  steel  has  certain  peculiarities  which  must  be 
understood  if  one  would  be  a  successful  hardener.  The 
outside  surface  of  a  bar  of  steel,  as  it  comes  from  the 
steel  mill  or  forge  shop,  is  decarbonized  to  a  consider- 
able depth.  This  is  because  the  action  of  the  oxygen 
in  the  air  causes  the  carbon  to  be  burned  out  of  the 
steel  at  the  surface  during  the  various  operations  when 
the  steel  is  red  hot.     In  order  that  the  decarbonized 


Decarbonized  surface  of  steel. 

portion  may  not  give  trouble,  it  is  necessary  to  cut 
away  enough  of  the  surface  to  remove  this  portion 
before  hardening.  If  a  tool  which  is  to  finish  ^  inch 
diameter  is  to  be  made  out  of  round  steel,  it  is  neces- 
sary to  select  stock  at  least  -jV  inch  diameter  larger  than 
the  finished  tool,  or  the  outer  surface  will  not  harden 
sufficiently.  For  sizes  from  ^  to  i  inch  diameter, 
select  stock  -^  to  }i  inch  larger.  For  sizes  from  i  to 
2  inches  diameter,  select  stock  from  }i  to  -^q  of  an  inch. 
For  sizes  above  2  inches,  about  ^  of  an  inch  should  be 
cut  off. 

It  is  necessary  when  centering  round  steel  to  have 
the  center  hole  very  near  the  center  of  the  stock,  as 
shown  in  Fig.  2,  in  order  to  take  off  an  equal  quantity 


Figure  2,  Figure  3. 

Proper  and  imnroper  centering. 

of  the  decarbonizing  surface  all  around.  If  a  piece  is 
centered,  as  shown  in  Fig.  3,  the  decarbonized  surface 
will  be  entirely  removed  from  one  side  of  the  piece 
and  scarcely  any  of  it  taken  from  the  opposite  side ; 
consequently,  the  side  from  which  it  was  removed 
will  be  hard,  while  the  opposite  side  will  not  harden, 
or  at  least  will  not  be   as   hard   as   the   other  side. 


Extravagant  economy. 

So  it  will  be  very  readily  seen  that  this  simple  fact, 
which  is  often  entirely  overlooked  in  machine  shops, 
is  a  cause  of  a  great  amount  of  trouble. 

Tool  makers,  as  a  rule,  understand  this  fact  in 
regard  to  steel,  but  some  one  in  authority,  wishing  to 
save  money  for  the  manufacturing  concern,  gives  the 
job  of  centering  to  the  "tool  room  kid, "  as  he  is  termed 
many  times.  He  fails  to  instruct  him  in  the  proper 
manner,  the  boy  does  not  understand  the  nature  of 
steel,  and  as  a  consequence,  it  is  centered,  as  shown  in 

Fig.  3- 

Now,  if  the  tool  maker  were  given  the  job,  he 
would  readily  see  that  it  was  centered  wrong.  But  the 
spirit  of  economy  still  prevails,  and  the  boy  is  allowed 
to  rough  out  the  piece.  As  a  consequence,  the  outside 
surface  is  removed,  and  all  traces  of  the  eccentric  cen- 
tering are  eliminated.  The  piece  is  made  into  a  reamer 
or  some  other  tool,  and  when  hardened  it  is  soft  on  one 
side,  the  other  side  being  hard  enough.  There  is  no 
one  that  can  be  blamed  but  the  hardener,  so  he,  poor 
fellow,  has  to  "catch  it."  It  wouldn't  be  human 
nature  to  stand  by  and  say  nothing  when  blamed  for 
something  one  didn't  understand,  so  he,  in  turn,  says 
the  steel  is  no  good. 

As  a  consequence,  the  make  of  steel  is  often 
changed  and  another  kind  is  procured,  and  as  it  is 
desirable  to  test  the  steel  before  making  any  quantity  of 
it  into  costly  tools,  the  tool  maker  is  told  to  cut  off  a 
piece  of  the  stock  and  make  a  reamer  just  like  the 
one  that  wouldn't  harden  properly.  He  centers  the 
piece,  as  shown  in  Fig.  2,  turns  it  to  size,  cuts  the  teeth 
and  gets  it  ready  for  hardening.  It  comes  out  all 
right.     The  steel  is  pronounced  O.  K.  and  a  supply  is 


No  mysteries  in  steel  handling. 

ordered.  A  large  batch  of  reamers  is  made  up  and  the 
same  boy  is  given  the  job  of  centering  and  **  roughing  " 
them,  and  the  results  are  the  same  or  worse  than  when 
the  former  lot  was  hardened.  Now,  it  is  evident  to 
every  one  that  the  hardener  must  be  to  blame.  He 
hardened  one  reamer  from  this  same  steel  and  it  was 
satisfactory.  Well,  the  only  conclusion  is  that  he  made 
a  mistake  when  he  did  that  one^  and  isn't  on  to  his  busi- 
ness, so  he  is  nagged  and  found  fault  with  until  he  can 
stand  it  no  longer  and  gets  out.  The  next  man  has 
the  same  results,  and  those  in  charge  say,  *  *  You  can't 
get  a  decent  hardener  now-a-daj^s. "  All  this  trouble 
and  expense  because  some  one  wanted  the  reputation 
of  being  a  good  manager. 

Now,  a  boy  can  center  and  rough  out  stock  and  do 
it  all  right,  but  he  must  be  told  how  and  he  must  be 
watched.  If  a  make  of  steel  that  gives  satisfaction 
suddenly  shows  freaks,  do  not  at  first  condemn  the 
steel,  but  look  for  the  cause.  Many  people  have  the 
idea  that  there  are  unaccountable  mysteries  connected 
with  tool  steel,  and  that  hardening  is  a  thing  which 
must  be  attended  with  luck,  or  bad  results  follow. 
Now,  as  a  matter  of  fact,  if  a  good  steel  is  used,  the 
cause  may  be  found  for  all  troubles  which  occur  when 
it  is  hardened,  and  many  times  they  will  be  found  to 
result  from  some  penny  wise  and  pound  foolish  notion. 

Another  peculiarity  of  steel  is  that  if  the  position 
of  any  of  its  molecules  is  disturbed  when  the  steel  is 
cold,  there  is  apt  to  be  trouble  when  the  piece  is 
hardened.  For  instance,  if  a  piece  of  steel  that  is  to 
be  hardened  for  any  given  purpose  is  cut  from  a  bar 
of  tool  steel  and  it  is  found  to  be  so  bent  that  it  would 
be  impossible  to  turn  and  make  straight  and  remove 


Steel  of  difFerent  makes  vary. 

all  the  decarbonized  surface,  the  piece  should  be  heated 
red  hot  and  straightened.  If  it  were  straightened  cold, 
then  finished  to  size  and  hardened,  it  would  be  almost 
sure  to  spring.  The  writer  has  seen  men  at  work 
making  blanking  dies  for  punching  press  work  who, 
when  they  made  the  openings  too  large  at  any  point, 
would  take  a  hammer  and  pene  the  stock  into  the 
opening  without  heating  the  die.  They  would  plane 
the  top  of  the  die  for  shear  and  then  finish  it  and  swear 
about  the  hardener  when  the  piece  cracked  in  harden- 
ing directly  under  where  they  pened.  Possibly,  it 
would  not  show  any  bad  results  at  that  time,  but 
when  the  die  was  used,  the  portion  referred  to  would 
crack  off.  Or  if  the  punch  were  a  tight  fit,  it  would 
lift  a  piece  of  steel  from  the  face  of  the  die  the  shape 
of  the  hammer  pene  or  of  the  set  used. 

Steels  of  different  makes  vary  in  their  composition. 
A  successful  hardener  will  experiment  with  a  new  steel 
and  find  out  just  what  he  can  do  with  it.  One  make  of 
steel  will  harden  at  an  extremely  low  heat ;  another  make 
will  not  harden  in  a  satisfactory  manner  at  that  heat. 
It  requires  a  higher  heat  in  order  to  harden  it.  Now, 
if  we  were  to  heat  the  first  steel  as  hot  as  we  were 
obliged  to  heat  the  other,  we  should  ruin  it,  or  at  least 
harm  it.  For  this  reason  it  is  not  advisable,  generally 
speaking,  to  have  a  half  a  dozen  different  kinds  or 
makes  of  steel  around  a  shop,  unless  someone  knowing 
the  nature  and  peculiarities  of  each  is  to  do  the  harden- 
ing. And  even  then  trouble  will  follow  unless  a  ticket 
accompanies  each  tool  stating  the  kind  of  steel,  and 
this  in  the  ordinary  machine  shop  would  lead  to  end- 
less confusion. 

A  steel  which  gives  satisfactory  results  should  be 

a6 


Steel  is  usually  all  right. 

selected  and  then  used  until  convinced  that  some- 
thing better  is  to  be  had.  The  judgment  of  an  ex- 
perienced hardener  is  not  always  to  be  relied  upon  as 
to  the  best  brand  of  steel  for  a  particular  purpose.  It 
may  be  that  he  has  had  excellent  results  with  a  certain 
brand  because  he  has  methods  of  hardening  particularly 
fitted  to  that  brand  of  steel;  but  it  may  be  true  that 
were  he  to  change  his  methods  to  adapt  them  to 
another  steel,  much  better  results  would  follow. 

The  writer  was  at  one  time  brought  in  contact 
with  a  hardener  whose  complaints  in  regard  to  the 
steel  furnished  had  caused  the  superintendent  of  the 
shop  to  change  the  make  of  steel  several  times.  Each 
time  a  new  steel  came  into  the  shop  the  result  was  the 
same,  until  finally  by  the  advice  of  one  of  the  steel  manu- 
facturers several  tools  similar  to  those  previously  hard- 
ened with  unsatisfactory  results  were  made  from  each 
of  the  condemned  steels  and  given  to  a  man  who  was 
considered  an  expert  hardener.  When  they  were  hard- 
ened and  returned  they  were  all  found  to  be  in  a  satis- 
factory condition,  not  a  crack  visible  in  any  of  them. 
They  all  gave  good  satisfaction,  proving  that  the 
man  rather  than  the  steel  was  at  fault. 

Almost  any  of  the  leading  makes  of  steel  in  the 
market  will  give  good  results  if  treated  properly,  but 
the  same  treatment  will  not  answer  for  all  makes. 
Some  makes  are  more  satisfactory  than  others  for 
certain  purposes,  but  better  results  may  be  obtained 
from  most  of  them  than  is  often  the  case. 

Steel  may  be  purchased  in  bars  of  various  shapes. 
The  more  common  shapes  are  round,  square,  flat  and 
octagon.  If  steel  is  to  be  cut  from  the  bar  and  ma- 
chined to  shape,  it  is  advisable  to  purchase  bars  wliich 

»7 


The  choice  of  proper  steel. 

allow  of  machining  to  the  desired  shape,  at  the  least 
expense  and  with  as  little  waste  of  material  as  possible. 
Always  remember  that  it  is  necessary  to  remove  the 
decarbonized  portions  previously  mentioned. 

If  a  tool  which  is  to  be  cylindrical  in  shape  is  to  be 
made,  use  a  piece  of  round  steel.  If  an  article  which 
is  to  be  finished  square,  use  a  piece  of  square  steel,  etc. 

Steel  of  the  same  quality  and  temper  is  furnished 
in  all  the  common  shapes  on  the  market.  It  v/as  for- 
merly considered  necessary,  if  best  results  were  de- 
sired, to  use  octagon  steel  when  making  cylindrical 
pieces  of  work,  but  now  all  steel  makers  claim  to 
make  round  steel  of  exactly  the  same  quality  as  the 
corresponding  sizes  of  octagonal  shape,  and  the  exper- 
ience of  every  mechanic  who  has  tested  the  two  under 
similar  circumstances  substantiates  the  claim. 

The  steel  maker  puts  on  the  market  steel  of  dif- 
ferent tempers,  but  he  advocates  the  use  of  the  par- 
ticular temper  which  he  considers  best  adapted  to  the 
work  in  the  individual  shop.  As  a  rule  he  does  not 
make  any  mention  of  any  other  temper,  because  he 
knows  that  if  steel  of  several  different  tempers  are  kept 
in  stock,  that  in  all  probability  the  labels  will  be 
removed  in  a  short  time  and  any  distinguishing  marks 
be  thrown  away.  Then  no  one  in  the  shop  will  know 
one  temper  from  another,  and  when  a  piece  of  ^  per 
cent,  carbon  steel  is  made  into  a  shank  mill  or  similar 
tool,  and  a  piece  of  i  ^  per  cent  carbon  steel  is  made 
into  some  tool  that  must  resist  the  action  of  heavy 
blows,  trouble  will  follow  and  the  steel  be  condemned. 
For  this  reason  it  is  considered  advisable  to  advocate 
the  use  of  a  temper  that  will  give  satisfactory  results 
when  put  to  most  uses.     But  the  fact  remains  that 

aS 


Carbon  necessary  to  proper  results. 

steel,  in  order  to  give  best  results,  should  contain  the 
proper  percentage  of  carbon  for  use  on  the  particular  job. 
In  shops  where  detail  is  followed  very  closely,  the 
steel  is  kept  in  a  stock-room,  each  different  temper  by 
itself,  and  so  marked  that  there  is  no  danger  of  it  get- 
ting mixed.  Much  better  results  are  then  obtained, 
provided  a  competent  man  does  the  hardening,  than  if 
one  temper  was .  used  for  everything.  But  in  a  shop 
where  there  is  only  one  rack,  and  sometimes  no  rack, 
the  stock,  machinery  steel,  tool  steel,  and  everything 
else  is  kept  on  this  one  rack,  or  in  a  pile  on  the  floor,  it 
is  not  advisable  to  have  steel  of  different  tempers 
lying  around,  or  results  anything  but  satisfactory  are 
sure  to  follow. 


Percentage    of  Carbon   Necessary  to   Produce 
Desired  Results. 

In  the  first  part  of  this  section  is  given  a  table  of 
percentages  of  carbon  present  in  steel  for  various  pur- 
poses. This  table  is  generally  accepted  as  a  guide  to 
those  desiring  steel  for  any  given  purpose,  and,  gen- 
erally speaking,  it  is  safe  to  use  stock  of  the  tempers 
given,  but  modem  competition  has  made  it  necessary 
to  harden  steel  harder  and  yet  have  it  able  to  stand 
more  than  was  formerly  the  case.  When  these  condi- 
tions prevail,  it  is  necessary  many  times,  especially  in 
the  case  of  cutting  tools,  to  use  steel  having  a  higher 
percentage  of  carbon  than  is  given  in  the  table. 

When  steel  containing  a  higher  percentage  of  car- 
bon is  used,  then  extra  care  must  be  observed  when 
heating.     For  the  operations  of  forging,  annealing,  or 

29 


No  one  steel  best  for  all  purposes. 

hardening  high  carbon  steels  should  not  tinder  any  cir- 
cumstances be  given  to  a  careless  workman,  or  to  one 
not  thoroughly  familiar  with  the  effects  of  heat  on 
steel  of  this  character. 

When  high  carbon  steels  are  used  and  treated 
properly,  they  will  do  more  work  than  steels  contain- 
ing a  lower  percentage,  but  unless  they  are  to  be 
handled  by  a  competent  man,  they  generally  prove  to 
be  a  very  unsatisfactory  investment. 

When  long  articles  which  are  to  be  hardened  are 
made  of  tool  steel,  the  writer  has  had  excellent  results 
by  taking  the  steel  as  it  came  from  the  bar,  or  after  it 
was  roughed  out  for  annealing,  or  even  after  it  was 
forged  in  the  smith's  shop,  by  heating  it  to  a  forging 
heat.  Then,  standing  it  on  end  on  the  anvil,  or  on  a 
block  of  iron  on  the  floor — if  it  were  long — and  giving 
it  one  or  more  blows  on  the  end  with  a  hand  hammer  or 
sledge;  the  weight  of  the  hammer  depending  on  the 
size  of  the  piece.  This  operation  is  sneered  at  by  many 
expert  steel  workers,  but  the  writer's  experience  con- 
vinces him  that  better  results  will  follow  when  the 
piece  is  hardened,  if  this  precaution  is  taken,  the  ten- 
dency to  spring  is  apparently  greatly  reduced.  Should 
the  piece  be  bent  by  the  operation,  it  should  be  straight- 
ened while  red  hot,  because  if  straightened  cold,  it  most 
surely  will  spring  when  hardened. 

The  writer  has  no  intention  of  advertising  any 
make  of  steel,  as  he  does  not  believe  any  one  make  is 
best  for  all  purposes,  but  experience  has  convinced  him 
that  some  makes  of  steel  give  better  results  for  certain 
purposes  than  others,  also  that  some  makes  are  better 
adapted  for  ♦*  all  around  "  use  than  others. 

If  a  party  is  using  a  steel  with  unsatisfactory 

3° 


Cheap  steel  not  necessarily  cheap. 

results,  it  is  advisable  to  take  measures  to  ascertain 
whether  the  trouble  is  in  the  steel,  or  in  the  method  of 
working  it.  The  writer  has  seen  one  of  the  best  steels 
on  the  market  condemned  and  its  use  discontinued, 
because  the  workman  who  did  the  hardening  had  been 
accustomed  to  a  steel  containing  a  lower  percentage  of 
carbon.  The  steel  he  recommended  was  adopted,  the 
results  so  far  as  hardening  were  concerned  were  satis- 
factory, but  the  tools  did  not  produce  nearly  the 
amount  of  work  they  should. 

After  a  time,  the  services  of  an  expert  were  sought. 
He  advocated  the  use  of  the  very  steel  they  had  dis- 
carded. A  tool  was  made  from  it,  the  expert  harden- 
ing the  tool.  When  put  to  actual  use,  it  proved  itself 
capable  of  doing  many  times  the  amount  of  work 
between  grindings  that  could  be  obtained  from  low 
carbon  steel. 

The  hardener,  like  a  sensible  man,  allowed  the 
expert  to  instruct  him  in  the  proper  methods  to  pursue, 
with  the  result  that  he  became  one  of  the  best  hardeners 
the  writer  has  ever  had  the  pleasure  of  meeting. 

A  steel  should  never  be  selected  because  it  is  cheap^ 
becaiise  it  often  happens  that  the  steels  which  sell  for  the 
least  money  are  the  dearest  in  the  end.  It  is  possible 
to  put  $100.00  worth  of  work  on  a  piece  of  steel  costing 
25  cents.  Now,  if  the  tool  was  found  useless  when 
hardened,  then  $100.25  ^^^  been  expended  in  vain. 
On  the  other  hand,  if  steel  adapted  to  the  purpose  had 
been  used,  and  it  had  cost  50  cents,  there  would  have 
been  a  clear  saving  in  money  of  nearly  $100.00.  This 
is  not  an  exaggerated  comparison,  as  such  cases  are 
frequently  met  with  by  the  writer. 

On  the  other  hand,  it  is  folly  to  pay  75  cents  a 

31 


"Pipes"  in  steel  bars. 

pound  for  steel,  when  i6  cents  will  buy  one  exactly- 
suited  to  the  job.  Good  steel  is  cheaper  at  any  price 
it  would  be  apt  to  bring  in  the  open  market,  than  steel 
not  adapted  for  the  purpose  would  be  if  it  were  a  gift. 
A  steel  not  adapted  to  the  purpose  is  dear  at  any  price. 

The  writer  has  had  charge  of  tool  rooms  employ- 
ing large  numbers  of  tool  makers,  and  experience  has 
convinced  him  that  it  is  a  saving  of  money  in  every 
case  to  test  every  bar  of  tool  steel  received  into  the 
shop  that  is  to  be  made  into  tools. 

If  the  steel  is  kept  in  the  stock-room,  the  stock 
keeper  can — when  the  hack  saw,  or  cutting  off  machine 
is  not  in  use — cut  a  piece  from  the  end  of  each  bar, 
stamping  the  piece  cut  off  and  the  bar  alike.  These 
pieces  can  be  given  to  an  experienced  hardener,  to 
heat  them  to  the  proper  hardening  heat,  and  quench 
them  in  a  bath  of  water  or  brine.  After  they  are 
thoroughly  dry,  break  as  near  across  the  center  as  pos- 
sible, examining  the  center  of  fracture  for  pipes.  A 
pipe  is  a  cavity  which  of  course  makes  the  bar  un- 
sound. It  may  run  the  entire  length  of  the  bar.  If  a 
bar  having  a  pipe  is  discovered,  the  steel  maker  will 
gladly  replace  it  with  a  sound  bar.  Any  make  of  steel 
is  liable  to  have  cavities  of  this  kind,  although  the 
inspector  at  the  mill  generally  discovers  it  in  the  ingot, 
thus  preventing  it  being  made  into  bars ;  but  it  some- 
times escapes  even  the  most  careful  inspection. 

If  a  tool  costing  $50.00  were  made  from  a  bar  that 
was  piped,  it  would  in  all  probability  go  all  to  pieces  in 
the  bath  when  hardened,  unless  the  tool  were  of  a 
character  that  allowed  the  piped  portion  to  be  re- 
moved. It  is  safer,  however,  to  inspect  the  bar  before 
any  costly  tools  are  made  from  it.     If  the  bar  proves 

3» 


Inspection  an  economy. 

sound,  the  grain  should  be  examined;  if  this  is  fine, 
and  of  the  proper  appearance,  it  may  be  tested  for 
hardness  with  a  file. 

If  the  piece  proves  to  be  all  right,  the  bar  may  be 
stamped  O.  K.  or  given  some  distinguishing  mark; 
should  it  prove  otherwise,  the  manufacturer  should  be 
notified  and  the  steel  returned  to  the  mill. 

This  system  of  inspection  may  seem  like  a  need- 
less waste  of  money,  but  the  cost  of  one  tool  which  is 
of  no  use  when  finished,  would  pay  the  necessary 
expense  of  testing  all  the  steel  used  in  a  machine  shop 
of  the  ordinary  size  in  five  years. 

When  a  tool  is  required  to  do  extra  hard  work,  that 
is,  cut  hard  stock,  or  run  at  a  higher  speed  than  is 
ordinarily  employed  in  the  shop,  it  is  advisable  to  get 
a  steel  having  a  greater  percentage  of  carbon  than  the 
steel  used  for  tools  for  ordinary  work.  When  high 
carbon  steels  are  bought,  they  should  be  distinctly 
labeled  or  stamped,  and  kept  by  themselves  away  from 
the  rest  of  the  steel,  because  if  the  identity  of  the 
piece  is  lost,  it  is  liable  to  be  made  into  tools  and  hard- 
ened without  the  hardener  knowing  that  it  differs  in 
composition  from  the  steel  ordinarily  used.  As  a  con- 
sequence he  would  heat  it  to  the  same  temperature  he 
was  accustomed  to  give  the  steel  regularly  used,  and  it 
would  in  all  probability  be  cracked  from  the  heat  which 
was  higher  than  was  necessary. 


33 


Methods  of  Heating. 


c-o 


The  method  employed  when  heating  steel  for  any- 
particular  purpose  depends  on  the  facilities  furnished 
by  the  individual  shop.  As  it  is  not,  generally  speak- 
ing, the  office  of  the  hardener  to  purchase  the  equip- 
ment of  the  shop ;  biit  to  use  such  equipment  as  may 
be  furnished  him,  it  is  necessary  that  he  adapt  himself 
to  circumstances  as  he  finds  them.  The  successful 
man  is  one  who  makes  the  best  use  possible  of  the 
equipment  furnished  him. 

If  there  are  but  a  few  tools  to  harden,  and  they  are 
of  a  character  that  could  be  treated  in  a  satisfactory 
manner  in  an  ordinary  blacksmith's  forge,  it  would  not 
be  considered  advisable  to  purchase  a  costly  furnace, 
even  though  it  were  known  that  the  work  could  be  done 
more  cheaply  per  piece,  because  the  limited  number  of 
pieces  would  not  warrant  the  extra  outlay  of  money  for 
equipment. 

On  the  other  hand,  if  work  was  to  be  done  in  large 
quantities,  it  would  be  wise  to  procure  the  necessary 
equipment  to  do  the  work  in  a  satisfactory  manner  at 
the  least  cost  possible.  If  the  total  amount  of  harden- 
ing done  in  a  shop  in  any  one  year  was  6  or  7  diamond 
point  turning  tools  and  2  or  3  side  tools,  it  would  be 
folly  to  invest  several  hundred  dollars  in  a  muffle  fur- 
nace and  an  elaborate  system  of  baths.  But  if  the  pro- 
duct of  the  shop  was  several  hundred  taps,  reamers  or 

34 


Hardener  should  do  his  best. 

similar  tools  per  day,  it  would  not  be  considered  gooJ 
business  policy  to  heat  tliem  for  hardening  in  an  ordin- 
ary blacksmith's  forge.  It  would  not  be  possible  to 
do  the  work  as  cheaply,  neither  would  it  be  done  in  as 
satisfactory  a  manner  as  though  apparatus  especially 
adapted  to  this  class  of  work  were  used. 

But,  as  previously  stated,  the  hardener  should  make 
the  best  possible  use  of  apparatus  furnished  him.  If 
obliged  to  use  a  blacksmith's  forge  for  heating  steel 
either  for  forging  or  hardening,  he  should  see  that  his 
fire  is  clean  and  that  it  is  high  enough  above  the  blast 
inlet  so  no  jet  of  air  can  strike  the  heated  steel. 

It  is  possible  to  heat  comparatively  small  articles 
in  a  satisfactory  manner  in  an  ordinary  forge  by  using 
care  in  regard  to  the  size  and  condition  of  the  fire  and 
the  location  of  the  piece  of  work  in  relation  to  the 
blast  inlet. 

It  is  always  advisable  to  build  a  fire  large  and  high 
enough  so  that  the  portion  of  the  piece  being  heated 
will  be  covered  to  a  considerable  depth  by  the  coals. 
Otherwise  the  action  of  the  oxygen  in  the  air  would 
cause  the  carbon  to  be  burned  out  of  the  surface  of  the 
steel,  leaving  it  decarbonized ;  in  this  condition  it  can- 
not harden. 

If  the  cold  air  from  the  blast  strikes  heated  steel, 
it  causes  it  to  crack,  particularly  if  there  are  teeth  or 
projections,  as  these  are  more  susceptible  to  the  action 
of  heat  and  cold  than  the  heavier  portions.  The  steel 
would  expand  from  the  action  of  the  heat,  the  air 
striking  the  projections  would  cause  contraction,  and 
the  repeated  expansion  and  contraction  would  cause 
the  steel  to  crack. 

If  large  pieces  are  to  be  hardened,  a  large  high 

S5 


Action  of  charcoal  on  steel. 

fire  should  be  built,  as  a  low  fire  in  a  forge  having  a 
tuyere — blast  inlet — of  the  ordinary  size  would  not  be 
sufficiently  large  to  heat  the  piece  uniformly.  It  is 
always  advisable  when  heating  large  pieces  to  use  a 
fire  of  new  coals  if  charcoal  is  used  as  fuel,  as  coals 
which  have  been  used  for  some  time  are  burned  to  the 
extent  that  the  fire  is  dead  unless  considerable  blast  is 
used,  in  which  case  the  result  would  be  a  lot  of  cracked 
work. 

Charcoal  is  generally  considered  the  ideal  fuel  to 
use  when  heating  tool  steel.  As  it  is  a  form  of  carbon, 
it  is  generally  given  credit  for  imparting  carbon  to  the 
steel  heated  in  it.  Now,  this  is  the  case,  if  low  carbon 
steels  are  packed  in  a  tube  or  box  with  a  good  quality 
of  charcoal,  away  from  the  action  of  the  fire  and  air, 
and  run  for  a  considerable  length  of  time.  Carbon  will 
then  be  absorbed  by  the  steel.  Before  the  process  of 
making  crucible  steel  was  discovered,  iron  bars  or  rods 
were  packed  in  tubes  with  charcoal  and  run  for  a  suffi- 
cient length  of  time  to  charge  the  iron  with  carbon, 
thus  making  a  union  of  iron  and  carbon,  or  steel,  as 
it  is  familiarly  known.  This  process  is  known  as 
"cementation." 

It  does  not  seem  probable  that  a  piece  of  tool  steel, 
high  in  carbon  would  absorb  any  extra  carbon  in  the 
brief  time  it  was  exposed  to  the  action  of  fire,  in  heat- 
ing for  hardening.  On  the  contrary,  if  a  piece  of  high 
carbon  steel  is  heated  in  this  manner,  it  is  apt  to  lose 
some  of  the  carbon  at  the  surface.  For  this  reason,  a 
piece  of  high  carbon  steel  is  not  so  liable  to  have  sur- 
face cracks  if  heated  for  hardening  in  a  charcoal  fire. 
But  from  experiments,  it  can,  I  think,  be  truthfully 
claimed  that  a  piece  of  1.5  per  cent,  carbon  steel  will 

36 


The  use  of  mufHe  furnaces. 

not  be  as  hard  on  the  surface  if  heated  in  a  charcoal 
fire,  as  if  heated  in  a  fire  burning  coke. 

But  if  steel  must  be  heated  in  a  fire,  exposed  to 
the  action  of  the  burning  fuel,  it  is  advisable  in  most 
cases  to  use  charcoal,  because  it  does  not  contain  im- 
purities injurious  to  the  steel. 

On  the  other  hand,  high  carbon  steel  will  not  be  as 
hard  on  the  surface  if  heated  in  a  charcoal  fire,  as  if 
heated  in  some  form  of  furnace  where  the  article  is  not 
exposed  to  the  action  of  the  burning  fuel,  and  as  most 
of  the  other  fuels  contain  impurities  injurious  to  the 
steel,  it  is  best  to  heat  in  a  manner  that  removes  it 
from  the  action,  not  only  of  the  burning  fuel,  but  also 
from  the  action  of  the  air.  In  order  to  accomplish  the 
desired  result,  the  article  may  be  placed  in  a  tube  or 
iron  box,  or  a  muffle  furnace  may  be  used. 

If  many  pieces  are  to  be  hardened,  it  is  advisable 
to  procure  a  furnace  especially  adapted  to  the  class  of 
work.  The  neatest,  most  easily  managed  furnace,  and 
the  one  which  gives  as  good  satisfaction  as  any,  is  a 
form  made  to  bum  illuminating  gas  as  fuel.  These 
can  be  procured  of  almost  any  size.  A  very  satisfac- 
tory style  of  this  type  is  known  as  a  muffle  furnace, 
from  the  fact  that  the  piece  of  steel  to  be  heated  is  placed 
in  an  oven  or  muffle.  The  flame  circulating  around 
the  muffle  heats  it  to  any  required  degree  of  heat. 
The  steel  is  heated  by  radiation,  consequently  it  is  not 
subjected  to  the  injurious  effects  of  the  products  of 
combustion;  and  as  the  door  may  be  closed,  there  is 
little  danger  of  oxidation  of  the  heated  surface.  If  the 
furnace  is  not  provided  with  some  means  whereby  the 
work  being  heated  may  be  readily  observed  without 
removing  the  door,  it  is  advisable  to  drill  one  or  two 

37 


Types  of  muffle  furnaces. 


one-incli  holes  in  the  door,  covering  them  with  mica. 
These  furnaces  are  by  far  the  most  satisfactory  for 
general  use  of  any  form  the  writer  has  used.     Figs.  4 

and  5  represent 
two  styles  of 
these  furnaces. 
If  it  is  not  con- 
sidered advis- 
able to  purchase 
a  furnace  of  this 
description  and 
one  is  to  be 
made  on  the 
premises,  it  is 
possible  to  make 
a  very  satisfac- 
tory furnace 
quite  cheaply. 
If  large  or  long 
pieces  are  to  be 
heated  and  a 
furnace  is  to  be 
made  of  a  type 
where  the  steel 
is  placed  in  con- 
t  a  c  t  with  the 
fuel,  it  is  advis- 
able to  use  char- 
coal, as  either 
coke  or  coal  do 

Figure  4.      Muffle  furnace  for  hardening.  ^^^   fumish  a 

satisfactory  means  of  heating  under  the  circumstances 
mentioned.     The  grate  should  be  made  the  size  of  the 

38 


'TheDerryCoUariCo.- 

Muffle  furnace  for  hardening. 


Types  of  muffle  furnaces. 

inside  of  the  furnace,  as  in  this  way  a  uniform  heat 
may  be  maintained  in  all  parts  of  the  furnace,  and  it 
will  not  be  necessary  to  use  a  blast.  A  natural  draft 
will  be  found  sufficient. 

Fig.  6  shows  a  furnace  of  the  type  mentioned,  the 
dimensions  depending  on  the  size  and  character  of  the 
work  to  be  heated. 
A  damper  should  be 
placed  in  the  smoke 
pipe  in  order  to  check 
the  fire  if  there  is 
danger  of  its  becoming 
too  hot.  This  damper 
should  not  be  of  the 
type  usually  put  in  the 
pipe  of  a  coal  stove,  as 
these  dampers  are  made 
with  a  hole  to  allow  for 
the  escape  of  gas.  It  is 
not  desirable  to  have 
this  hole  in  the  damper, 
as  it  is  impossible  to 
check  the  fire  on  a 
windy  day.  The  lower 
door  must  also  be  fur- 
nished with  a  damper, 
in   order   to    furnish 


Figure  5.      Muffle  furnace  for  hardening. 


draft  when  desired.     It  is  possible  with  this  furnace 
to  do  very  excellent  work. 

If  it  is  desirable  to  build  a  muffle  furnace,  one 
may  be  made  to  use  either  charcoal,  coke,  or  hard  coal 
as  fuel  by  taking  the  one  represented  in  Fig.  7  as  a 
model,  and  changing  the  design  to  meet  the  require- 


39 


"Home-made"  muffle  furnaces. 

ments.  The  interior  of  the  muffle  is  represented  by  A, 
B  is  the  fire  box,  C  the  ash  pan.  The  heat  and  smoke 
passing  up  from  the  fire  box  follow  the  direction  of  the 
arrow  passing  under  the  muffle  and  out  of  the  smoke 
pipe  at  D.     A  damper  should  be  placed  in  the  smoke 


Figure  6.     A  '*home-made"  furnace. 

pipe  and  one  in  the  ash  chamber  door.  By  means  of 
these  dampers  the  draft  can  be  regulated  very  nicely. 
This  form  of  furnace  works  very  nicely  in  heating 
dies  and  similar  work. 

When  small  articles  are  hardened  in  large  quan- 
tities a  furnace  may  be  made  of  the  design  shown  in 

40 


"Home-made"  muffle  furnaces. 

Fig.  8,  where  a  represents  the  fire  box  which  bums 
hard  coal,  charcoal  or  coke ;  b  the  ash  box ;  and  c  the 
chamber  for  heating  the  work.  The  front  plate  has  a 
number  of  holes  corresponding  to  the  number  of  tubes 
it  is  considered  advisable  to  heat  at  a  time.  The  tubes 
are  made  by  taking  a  gas  pipe,  plugging  one  end  as 


The  Derry  Oollard  Co. 

Figure  7.     A  "home-made"  furnace  for  burning 
charcoal,  coke  or  hard  coal. 

shown  as  Fig.  9,  the  other  end  being  left  open.  A 
number  of  pieces  of  work  may  be  placed  in  each  tube 
and  the  tubes  placed  in  the  openings.  The  tubes  at 
the  bottom  will  heat  more  quickly  than  those  at  the 
top,  so  it  is  advisable  when  a  tube  in  the  bottom  row 
is  taken  from  the  furnace  to  fill  its  place  with  one  from 
one  of  the  top  rows.  The  tubes  as  they  are  filled  may 
be  placed  in  the  top  rows  and  allowed  to  heat  gradually 


41 


"Home-made"  muffle  furnaces. 

and  later  removed  and  placed  in  the  lower  row.      By 
following  this  plan  it  is  possible  to  heat  the  work 


o  o  o   o 

o   o   o 
o   o  o  o 


liw  Ddrry  CoUard  Co. 


Figure  8.     A  "home-made"  furnace  for 
heating  small  pieces. 


gradually  and  yet  harden  a  large  amount  of  work  in  a 

given  time.     The  tubes  should  be  turned  occasionally 

in  order  to  insure  even  heating  and  satisfactory  results. 

When  but  a  few  small  pieces  are  to  be  hardened 


*f/w/////ww///w///^vw.'//WA'w;/w////w//////w/w///^^^^^ 


The  Derry  ColUrd  Co. 

Figure  9.      Construction  of  tubes  in 
"home-made"  furnace. 

a  gas  blast  of  the  form  shown  in  Fig.   lo  answers  very 
nicely.     If  the  pieces  are  of  a  size  that  guarantee  their 


42 


Apparatus  for  heating  small  number  of  pieces. 

heating  quickly  it  is  safe  to  hold  them  in  the  flame, 
having  a  piece  of  fire  brick  to  reflect  the  heat.  By 
this  means  the  heat  is  utilized  to  much  better  advan- 
tage than  if  nothing  were  placed  back  of  the  work.     It 


Tlw  Deny  C«U*rd  C5o, 
Figure  lo.     Gas  blast  for  heating  a  few  pieces. 

is  possible  by  forming  a  cavity  in  the  brick  or  making 
a  small  oven  as  shown  in  Fig.  1 1  to  heat  a  much  larger 
piece  of  work  in  an  ordinary  blow  pipe  than  would 
otherwise  be  the  case. 


Figure  x  i .     Another  form  of  gas  blast  for  heating 


A  crude  but  satisfactory  method  of  economically 
heating  small  pieces  is  furnished  by  the  idea  presented 
in  Fig.  12,  in  which  case  a  small  oven  is  built  of  fire 
brick,    or    a    casting    of   the    desired    shape    may   be 


43 


Gas  blasts  for  heating  a  few  pieces. 

obtained.     In  either  case  a  flame  from  gas  blast  should 
enter  at  one  or  both  sides  through  holes  provided. 

Small  articles  may  be  heated  by  using  a  Bunsen 


Figure  12.      Small  "home-made"  gas  blast  oven. 


burner,  as  shown  in  Fig.  13,  which  can  be  applied  to  a 
gas  pipe  in  place  of  the  ordinary  burner,  or  may  be 
connected  by  means  of  a  piece  of  rubber  tube.  When 
using  a  burner  of  this  description  the  work  can  be 
heated  more  readily  if  a  piece  of  sheet  iron  is  placed 
over  the  burner  at  the  proper  height,  the  article  to  be 
heated  being  placed  beneath  this,  the  sheet  metal 
reflecting  the  heat  and  thus  increasing  its  utility. 

It  is  also  possible  by  means  of  a  blow  pipe  to  heat 
very  small  articles  sufficiently  for  hardening  by  means 
of  an  ordinary  gas  jet  or  the  flame  of  a  spirit  lamp,  as 
shown  in  Fig.  14.  This  is  an  expensive  method  when 
work  is  heated  in  quantities,  but  answers  very  nicely 
for  one  or  two  pieces. 

When  heating  for  forging  or  any  work  where  the 
outside  of  the  steel  is  afterwards  to  be  removed  it  is 


Heating  small  articles. 


advisable  to  use  a  form  of  furnace  where  the  direct 
heat  of  the  fire  comes  in  contact  with  the  steel,  as  it  is 
much  more  economical  and  is,  generally- 
speaking,  a  quicker  method  than  heating 
in  a  muffle  furnace.  It  is  advisable  many- 
times  when  heating  large  pieces  of  steel 
for  hardening,  to  use  a  furnace,  as  de- 
scribed, on  account  of  economy.     In  case 


/, 


The  Derry  CoUard  Co. 

Figure  14.      The  blow  pipe 
way  of  heating. 

the  outer  decarbonized  surface  is  to  be 
ground  away,  the  results  will  be  satisfactory ; 
but  if  the  outer  surface  must  be  hard,  then 
it  is  necessary  to  protect  the 
surface  from  the  action  of 
the  products  of  combustion. 
This  may  be  accomplished 
by  several  different  methods. 


The  Derry  CoUard  Co 

Figure  13.     Bunsen  burner,  for 
heating  small  articles. 


45 


Covering  paste,  and  how  to  make  it. 

One  method  is  to  place  the  portion  of  the  piece,  which 
must  not  be  decarbonized,  in  a  box  with  carbonaceous 
materials — as  charcoal  or  charred  leather — and  subject 
to  heat  until  the  piece  has  reached  the  desired  uniform 
temperature,  being-  careful  that  the  part  which  is 
exposed  to  the  direct  heat  of  the  fire  does  not  get 
over-heated. 

Another  method  which  is  used  when  an  article 
must  be  hard  on  all  its  surfaces  is  to  cover  the  piece 
with  a  carbonaceous  paste,  consisting  of  the  following 
ingredients : 

Pulverized  charred  leather 2  parts. 

Fine  family  flour 2      *' 

Fine  table  salt i  part. 

Mix  thoroughly  while  in  a  dry  state.  Water  is  then 
added  slowly  to  prevent  lumps ;  enough  water  may  be 
added  to  make  it  of  the  desired  consistency,  which 
depends  on  the  nature  of  the  work  and  the  length  of 
time  it  must  be  exposed  to  the  action  of  the  fire.  If 
the  articles  are  small  and  will  heat  to  the  proper  temp- 
erature for  hardening  in  a  few  minutes,  it  should  be  of 
the  consistency  of  varnish.  If,  however,  the  pieces  are 
large  and  require  considerable  time  for  heating,  it  must 
be  made  thicker. 

Various  substances  are  heated  red  hot  in  crucibles 
or  iron  dishes,  and  pieces  to  be  hardened  are  heated  in 
them.  These  exclude  the  air  and  so  prevent  oxidation 
and  decarbonization  of  the  surface  of  the  steel.  Among 
the  substances  used  are  lead,  tin,  glass,  cyanide  of 
potassium,  a  mixture  of  salt  and  cyanide  of  potassium. 

Lead  is  heated  in  a  crucible  in  a  furnace  of  the 
forms  shown  in  Figs.  15,  16.    It  furnishes  a  very  excel- 

46 


Heating  in  molten  lead. 

lent  means  of  heating-  work  which  is  hardened  in  large 
quantities.  When  making  furnaces  to  heat  lead  red 
hot  for  use  in  hardening  steel,  some  means  should  be 
provided  for  carrying  off  the  fumes  of  the  lead,  as  they 

are  very  injuri- 
ous to  the  work- 
man. They  are 
especially  hard  to 
dispose  of,  as 
they  are  heavier 
than  the  atmos- 
pheric air ;  conse- 
quently  cannot 
be  disposed  of  as 
readily  by  means 
of  a  ventilating 
shaft  as  other 
fumes.  It  is  nec- 
essary to  furnish 
a  pipe  connected 
with  an  exhaust 
fan.  This  pipe 
may  be  at  the  back  of  the  furnace  instead  of  over  it,  as 
is  generally  the  case  when  gases  or  smoke  are  to  be 
carried  off.  It  should  not  be  arranged  in  a  manner 
that  will  cause  the  surface  of  the  lead  to  become 
cooled  by  a  current  of  air  passing  over  it. 

If  illuminating  gas  can  be  procured  at  a  reasonable 
rate,  it  furnishes  an  ideal  method  of  heating  a  crucible 
of  lead.  Furnaces  burning  illuminating  gas  can  be  pro- 
cured of  a  size  and  shape  adapted  to  the  work  to  be 
done.  If,  however,  it  is  considered  advisable  to  make 
a  furnace  for  this  purpose,  one  may  be  made  which 


The  Derry  Collard  Co. 

Figure  15.      Lead  hardening  furnace. 


47 


Heating  in  molten  lead. 

will  give  good  satisfaction.  It  can  be  made  to  bum 
oil,  coal,  charcoal  or  coke.  If  oil  is  the  fuel  to  be  used, 
it  is  advisable  to  install  a  system  especially  for  this 
method,  and  as  circulars  and  full  explanations  can  be 


The  Derry  Collard  Co. 

Figure  i6.      Lead  furnace  for  hardening. 


procured  from  manufacturers  who  make  these  outfits, 
it  would  not  be  wise  to  go  into  their  details  here. 

If  it  is  considered  advisable  to  make  a  furnace 
burning  charcoal,  hard  coal  or  coke,  the  design  shown 
in  Fig.  17  may  be  used  or  changed  to  adapt  it  to 
these  fuels.  The  outer  shell  may  be  made  of  cast 
iron,  although  it  may  be  possible  to  procure  an  old 

48 


^Home-made"  lead  heating  apparatus. 


BACK  HALF.  TOP  PLATE 


FRONT  HALF 


boiler,  which  can 
usually  be  bought 
very  cheaply.  A 
piece  the  desired 
length  may  be  cut 
from  this,  that  an- 
swers the  purpose 
very  nicely.  A  round 
grate  and  the  neces- 
sary frame  to  support 
it  may  be  procured 
from  a  stove  dealer. 
The    form    of    grate 


mill  I  ■    'Hill 


2:^ 


Figure  1 7.      Coal,  coke  or  charcoal  furnace  for  lead  heating. 
49 


"Home-made"  lead  heating  apparatus. 

used  in  the  ordinary  cylinder  parlor  stove  will  answer 
every  purpose.  The  frame  should  be  attached  to  the 
shell  or  blocked  up  from  the  bottom  of  the  ash  box,  to 
allow  the  grate  to  be  turned  in  dumping  the  contents  of 
the  furnace.  The  interior  of  the  furnace  may  be  made 
of  circular  fire  brick,  which  may  be  supported  by  the 
slab  which  forms  the  base  or  bottom  of  the  ash  box  and 
designated  as  the  bottom  plate.  In  case  fire  brick  are 
used,  the  grate  frame  may  be  built  into  the  brick  work 
as  shown.  If,  however,  a  stove  lining  of  the  desired 
size  can  be  procured,  the  bricks  need  extend  only  up 
to  the  frame,  the  lining  extending  from  the  frame  to 
the  top  of  the  shell.  It  is  necessary  to  cut  an  opening 
in  the  ash  box  in  the  front  of  the  shell.  This  should 
be  covered  with  a  swinging  door,  containing  a  sliding 
damper.  This  door  is  necessary  in  order  to  remove 
the  ashes. 

A  smoke  pipe  must  be  provided  to  carry  off  the 
smoke  and  gas  from  the  fire.  This  should  be  con- 
nected with  the  shell  at  the  top  on  the  back  side  of  the 
furnace.  Over  the  top  of  the  furnace  must  be  placed 
a  plate,  having  a  hole  in  the  center  about  one  half  inch 
larger  than  the  size  of  the  crucible  to  be  used.  This 
plate  should  be  cast  in  two  pieces,  having  more  than 
one-half  of  the  hole  in  the  part  that  goes  at  the  back. 
The  smaller  or  front  half  may  be  moved  forward,  thus 
affording  an  opening  to  feed  the  coal  to  the  fire.  The 
object  in  having  more  than  one-half  the  opening  in  the 
back  part  of  the  cover  is  to  prevent  the  crucible  from 
tipping  over  when  the  front  plate  is  removed,  when 
there  is  not  sufficient  coal  in  the  furnace  to  support  it. 
It  is  necessary  to  place  a  piece  of  fire  brick  in  the 
center  of  the  grate  for  the  crucible  to  rest  on  in  order 

so 


Cyanide  of  potassium  furnace. 


that  the  fire  may  be  beneath  it.  The  smoke  pipe 
should  be  provided  with  a  damper,  to  enable  the 
operator  to  properly  control  the  fire.     This  form  of 

furnace  gives 
best  satisfaction 
when  hard  coal 
is  used  as  fuel. 

Red-hot  c  y  a  - 
nide  of  potassium 
is  used  with  ex- 
cellent results  in 
heating  tools  for 
hardening.  It 
not  only  heats  the 
steel  uniformly, 
but,  being  lighter 
than  steel,  the 
latter  sinks  in  the 
fluid,  thus  effect- 
ually excluding 
the  air  from  the 
surface  of  the 
steel.  It  also  has 
the  effect  of  mak- 
ing the  surface 
somewhat  harder 
than  it  otherwise 
would  be,  without 
making  the  steel 
more  brittle. 

It  should  be 
borne  in  mind 
that    cyanide    of 


Derryt3ollard  Co, 

Figure  1 8.      Furnace  for  heating  in 
cyanide  of  potassium. 


51 


Heating  cyanide  by  gas  furnace. 

potassium  is  a  violent  poison,  and  great  care  should  be 
exercised  in  its  use.  Not  only  is  it  poisonous  when 
taken  into  the  stomach,  but  the  fumes  are  highly  in- 
jurious to  the  workman  if  inhaled.  However,  if  fur- 
naces are  properly  designed  and  set  up,  the  fumes  may 
be  disposed  of  in  a  manner  that  does  away  with  this 
trouble. 

In  Fig.  1 8  is  shown  a  form  of  furnace  made  es- 
pecially for  use  in  heating  in  cyanide  of  potassium. 
The  fuel  used  is  illuminating  gas,  the  products  of 
combustion  passing  up  the  pipe  E  to  the  main  pipe  F 
which  also  conveys  the  fumes  of  the  melted  cyanide 
into  the  chimney  or  ventilating  shaft.  The  burners 
enter  the  furnace  at  A  and  heat  the  crucible  B,  which 
contains  the  cyanide.  A  hood  C,  which  is  provided 
with  a  door  D,  keeps  the  fumes  from  entering  the 
room  as  they  are  conveyed  into  the  pipe  F.  The 
lighting  holes  G  G  are  closed  by  the  plugs  shown 
when  the  fire  is  well  under  way. 

When  a  comparatively  small  number  of  small 
pieces  are  to  be  hardened,  it  is  possible  to  heat  the 
necessary  amount  of  cyanide  in  a  small  iron  dish  in  an 
ordinary  forge.  The  pieces  may  be  held  in  this  until 
the  desired  effect  has  been  accomplished,  when  they 
may  be  quenched. 

As  the  work  heated  in  this  manner  is  usually  hung 
from  the  edge  of  the  crucible  by  means  of  wire  hooks, 
it  is  generally  considered  advisable  to  use  a  square 
crucible  rather  than  a  round  one  when  work  is  done 
in  large  quantities. 

When  a  furnace  is  to  be  made  for  this  purpose,  the 
form  represented  in  Figs.  19-20  will  be  found  to  give 
good  results.    This  furnace  burns  hard  coal.     The  cruci- 

52 


"Home-made"  cyanide  furnace. 

ble  which  is  made  of  cast  iron  is  square  in  shape  and 

hangs  from  the  flange, 
which  is  cast  around 
the  upper  edge.  The 
top  of  the  crucible  is 
below  the  top  of  the 
back  of  the  furnace. 
An  opening  into  this 
allows  the  fumes  to  es- 
cape into  the  chimney. 
A  quantity  of  salt 
is  placed  in  a  crucible 
and  heated  red  hot. 
To  this  is  added  cya- 


Figures  19-20.      A  "home-made' 
cyanide  heating  furnace. 


Crucible 


??vi???7?????rr;rrr<t;rfW?? 


Fire  Box 


Grate 


Ash  Box 


nide  of  potas- 
sium  until 
the  steel 
heated  in 
it  shows 
the  proper 
amount  of 
hardness. 
This  method 
is  used  by 
manufactur- 
ers of  taps 
and  similar 
tools,  who 
claim  excellent  results  by  its  use.     The  same  general 

53 


The  Derry  Collard  Co. 


Where  furnaces  should  be  located. 

remarks  apply  to  this  metliod  as  to  heating  in  cyanide 
of  potassium. 

Glass  heated  in  a  crucible  until  it  is  red-hot  is  the 
means  used  by  some  watch  makers  to  heat  the  hair 
springs  of  the  watches.  It  is  claimed  that  the  nature 
of  steel  heated  in  this  manner  will  not  change  in  the 
least. 

Very  little  attention  is  paid  in  most  shops  to  the 
location  of  the  forge  or  furnace  used  in  heating  steel ; 
generally  any  out-of-the-way  place  is  selected.  If 
there  is  any  portion  of  the  shop  that  cannot  be  utilized 
for  anything  else,  it  is  given  up  to  this  purpose. 

The  fire  for  heating  steel  should  receive  more  con- 
sideration, so  far  as  location  is  concerned,  than  almost 
any  other  part  of  the  equipment.  It  should  never  be 
located  where  the  direct  rays  of  the  sun  or  any  strong 
light  can  shine  in  it,  or  in  the  operator's  eyes,  for  un- 
even results  will  surely  follow.  It  should  never  be 
located  in  or  near  a  window,  neither  should  the  roof  be 
constructed  with  skylights  which  allow  any  of  the 
sun's  rays  or  any  strong  light  to  enter  the  portion  of 
the  room  where  the  furnace  is  located. 

An  ideal  place  for  the  location  of  a  furnace  used  in 
heating  steel  for  hardening,  is  in  a  room  so  constructed 
that  no  rays  of  sunshine  or  direct  light  can  enter  it. 

It  is  extremely  important  that  due  consideration 
is  given  the  subject  of  ventilation.  Some  means 
should  be  provided  whereby  pure  air  can  be  freely 
supplied  without  creating  drafts,  which  would  cause 
the  operator,  who  is  perspiring  freely,  to  take  cold. 
The  room  should  be  so  located  that  it  will  not  be  damp, 
or  the  health  of  the  workman  would  be  hazarded. 

Too  often  in  the  past  the  precautions  noted  have 

54 


Heating  tool  steel. 

received  very  little  consideration,  because  those  in 
charge  did  not  realize  the  importance  of  a  properly 
equipped  or  located  room  in  which  to  do  this  class  of 
work. 


Heating  Tool  Steel. 


CO 

Tool  steel  is  very  sensitive  to  the  action  of  heat. 
A  slight  difference  in  temperature  after  a  piece  has 
reached  the  proper  hardening  heat  will  be  noticeable 
in  the  grain  of  the  steel.  When  heating  for  hardening, 
the  lowest  possible  heat  that  will  give  the  desired 
result  should  be  used.  The  amount  of  heat  necessary 
to  produce  this  result  depends  on  the  make  of  the  steel, 
the  percentage  of  carbon  it  contains,  the  percentage  of 
other  hardening  elements  that  may  be  in  the  steel, 
the  size  of  the  piece,  and  the  use  to  which  it  is  to  be  put 
when  hardened — all  these  must  be  taken  into  con- 
sideration. A  steel  low  in  carbon  requires  a  higher 
heat  than  a  piece  of  high  carbon  steel  in  order  that  it 
may  be  as  hard.  A  small  tool  does  not  require  as  much 
heat  as  a  larger  one  of  the  same  general  outline.  A 
tool  with  teeth  or  other  projections  will  harden  at  a 
lower  heat  than  a  solid  piece  of  the  same  size  made 
from  the  same  bar  of  steel.  There  is  a  proper  heat  at 
which  a  piece  of  steel  should  be  hardened  in  order  to 
produce  the  best  results,  but  this  heat  varies^  as  pre- 
viously explained. 

If  two  milling  machine  cutters  were  made  from 

55 


Refining  heat,  and  what  it  means. 

two  different  makes  of  steel  the  writer  has  in  mind, 
and  were  heated  in  a  manner  that  would  give  excellent 
results  in  the  case  of  one,  the  other  would  not  harden 
satisfactorily.  Now,  were  the  operator  to  heat  both  to 
the  proper  hardening  heat  for  the  other  make,  the  first 
one  mentioned  would  be  unfitted  to  do  what  was 
expected  of  it.  Either  make  of  steel  would  give  good 
results  if  heated  to  its  proper  heat. 

The  commonly  used  expression  of  degrees  of  heat 
which  tool  steel  should  receive  is  a  cherry  red.  The 
writer  cannot  dispute  the  appropriateness  of  this  term, 
but  cherry  red  is  a  varying  color  when  applied  to  the 
hardening  heat  of  tool  steel,  and  also  when  applied  to 
cherries.  Mr.  Metcalf,  in  his  work  on  steel,  styles 
this  heat  as  the  refining  heat,  and  this  seems  to  express 
the  idea  nicely. 

Steel  should  be  heated  to  a  temperature  that,  when 
hardened  and  broken,  the  fracture  will  show  the  grain 
to  be  the  finest  possible,  and  the  steel  will  be  hard. 
Now,  if  we  heat  a  piece  from  the  same  bar  a  trifle 
hotter  and  break  it,  the  fracture  will  show  a  coarser 
grain.  The  hotter  the  piece  is  heated,  the  coarser  the 
grain  becomes ;  and  the  coarser  it  is,  the  more  brittle 
the  steel  is.  While,  to  be  sure,  steel  heated  a  trifle 
above  the  refining  heat  will  be  somewhat  harder  than  if 
heated  to  the  refining  heat,  yet  the  brittleness  more 
than  offsets  the  extra  hardness ;  and  if  it  is  to  be  used, 
it  will  be  found  necessary  to  draw  the  temper  in  order 
to  reduce  the  brittleness  to  a  point  where  it  is  practical 
to  use  the  tool. 

After  taking  the  necessary  means  to  reduce  the 
brittleness  as  described,  an  examination  of  the  tool 
will  reveal  the  fact  that  in  drawing  the  temper  we  have 

56 


The  use  of  test  pieces. 

softened  the  piece  to  an  extent  that  it  is  not  as  hard  as 
the  piece  hardened  at  the  refining  heat.  Neither  will  it 
do  anywhere  near  the  amount  of  work,  as  the  grain  is 
open  and  when  the  pressure  is  applied  in  the  operation 
of  cutting,  the  surface  caves  in  because  of  the  open 
grain.  The  surface  has  not  the  backing  it  would  have, 
were  the  grain  close  or  fine. 

A  method  which  the  writer  has  used  in  his  experi- 
ments and  also  in  demonstrating  the  effect  of  heat  on 
the  grain  of  steel  is  to  take  six  pieces  of  steel  that  can 


The  Derry  CoUard  Cw. 

Figure  2.1.      Test  pieces. 

be  readily  broken.  Cut  the  required  number  from  a 
bar  I  inch  to  i^  inches  diameter,  having  the  pieces 
about  ^6  of  an  inch  thick.  Now  heat  the  pieces  one  at 
a  time  in  a  furnace  so  situated  that  no  rays  of  the  sun 
or  any  strong  light  can  shine  either  into  the  fire  or  into 
the  eyes  of  the  operator.  It  is  advisable  to  have  the 
furnace  located  in  a  room  that  can  be  darkened  so  that 
it  is  neither  light  nor  extremely  dark,  but  it  must  be 
uniform  throughout  the  experiment.  Now  heat  one 
piece  until  it  shows  somewhat  red,  yet  a  certain  black 
is  discernible  in  the  center  of  the  piece.  Dip  into  the 
bath  and  work  it  around  well ;  leave  until  cold.     Now 

57 


What  test  pieces  will  show. 

heat  another  piece  until  it  shows  the  lowest  red  pos- 
sible throughout  with  no  trace  of  black.  Heat  the 
third  piece  a  trifle  hotter,  and  continue  to  heat  each 
piece  hotter  than  the  preceding  one  until  they  are  all 
hardened,  heating  number  6  to  what  is  familiarly- 
termed  a  white  heat. 

Previous  to  heating,  each  piece  should  be  stamped 
in  two  places,  as  shown  in  Fig.  21,  in  order  that  the 
pieces  may  be  broken  across  the  center,  as  indicated  by 
the  dotted  lines,  and  yet  the  halves  of  the  same  piece 
be  easily  recognized.  When  heating,  commence  with 
the  piece  marked  i,  and  heat  consecutively.  After 
hardening  them  all  at  the  different  heats,  dry  thoroughly 
in  saw  dust  or  by  any  means  whereby  the  surface  may 
be  made  perfectly  dry,  after  which  they  may  be  broken. 
This  can  be  done  by  screwing  the  piece  in  the  jaws  of 
a  vise,  putting  about  one  half  of  it  below  the  tops  of 
the  jaws.  With  a  hammer  the  upper  part  may  be 
broken  off,  being  careful  that  the  piece  does  not  fly  and 
strike  so  as  to  stain  the  walls  of  the  fracture ;  or  the 
part  projecting  above  the  vise  may  be  caught  between 
the  jaw^s  of  a  monkey  wrench  and  the  piece  broken. 

An  examination  of  the  piece  marked  Fig.  22  will 
show  it  to  be  somewhat  hardened.  The  grain  will  not 
be  especially  fine  and  will  have  a  peculiar  appearance. 
No.  2  will  be  very  hard  and  the  grain  will  be  very  fine. 
It  will  break  with  very  ragged  walls,  as  shown.  No.  3 
will  also  be  very  hard  and  the  grain  not  as  fine  as  No. 
2.  The  grain  of  No.  4  will  be  coarser  than  No.  3. 
No.  5  will  be  coarser  than  No.  4,  while  the  grain  of 
No.  6  will  be  extremely  coarse  and  the  steel  unfitted 
for  anything  but  the  scrap  heap. 

It  will  pay  any  man  who  is  desirous  of  learning  to 

S8 


C 
be 
o 


Temperatures  for  different  steels. 

harden  steel  properly  to  try  this  experiment.  The  steel 
will  cost  him  but  a  few  cents,  and  it  need  take  but  a 
short  time  to  heat  it ;  but  the  knowledge  gained  of  the 
action  of  heat  on  tool  steel  will  be  of  inestimable  value 
to  him,  as  he  can  readily  see  the  effects  of  proper  and 
improper  heating  on  the  structure  and  strength  of  steel. 

If  the  operator  notes  carefully  the  heats,  he  will 
be  surprised  at  the  difference  in  the  amount  of  force 
necessary  to  break  a  piece  of  steel  hardened  at  the 
refining  heat  and  one  heated  slightly  above  this  tem- 
perature, which,  in  fact,  is  hardly  discernible  to  the  eye 
in  the  light  of  an  ordinary  blacksmith's  shop.  The 
difference  in  the  strength  of  a  piece  hardened  at  the 
refining  heat  and  one  heated  to  2l/uII  red  is  especially 
noticeable.  In  the  former  case  it  seems  almost  impos- 
sible to  break  it  by  a  blow  of  a  hammer,  and  it  seldom 
can  be  broken  across  the  center,  so  great  is  the  adhesion 
between  the  molecules  that  make  up  the  piece  of  steel, 
while  in  the  case  of  a  piece  heated  to  a  full  red,  the 
piece  may  be  broken  easily,  as  compared  with  the 
other.  When  one  takes  into  consideration  the  fact  that 
the  ordinary  workman  heats  steel  when  hardening  to  a 
full  red  oftener  than  to  the  refining  heat,  it  is  wonder- 
ful that  the  results  obtained  are  as  satisfactory  as  they 
are. 

As  stated,  the  temperature  to  which  a  piece  of 
steel  must  be  heated  in  order  to  refine  it,  depends  on 
the  composition  of  the  steel.  Tests  of  different  steels 
have  led  authorities  on  this  subject  to  the  conclusion 
that  it  is  necessary  to  heat  a  piece  of  steel  to  a  tem- 
perature between  800°  and  1200°  Fahr.  in  order  that  it 
may  harden  when  plunged  in  a  cooling  bath.  Jaroli- 
neck  places  the  temperature   at  932°  F.   (500°  C.)  as 

59 


The  uniform  heating  of"  steel. 

determined  by  experiments  made  by  him,  while  other 
authorities  claim  best  results  when  the  steel  was  heated 
to  1200°  F.  (about  650°  C).  As  this  difference  (268°  F.) 
involves  a  wide  range  of  heat,  it  is  evident  that  steels 
containing  different  percentages  of  carbon  were  used 
in  the  various  tests. 

If  a  piece  of  steel  be  heated  to  the  refining  heat  and 
then  quenched  as  soon  as  the  heat  is  uniform  through- 
out the  piece,  the  steel  is  in  the  best  condition  possible 
for  most  uses.  It  should  be  quenched  as  soon  as  it  is 
uniformly  heated  to  the  proper  temperature.  If  sub- 
jected to  heat  after  it  reaches  this  temperature,  it  will 
become  somewhat  hotter.  In  fact,  it  has  been  ascer- 
tained by  experiment  that  after  steel  is  heated  to  a  low 
red  the  temperature  may  be  raised,  and  the  difference 
in  the  heat  not  be  discernible  to  the  eye.  For  this 
reason  it  is  advisable,  if  best  results  are  desired,  to 
quench  as  soon  as  the  desired  unifor?n  heat  is  attained. 

It  is  also  important  that  steel  should  be  heated 
uniformly.  If  a  square  block  be  heated  so  that  the 
center  is  of  the  proper  heat  and  the  ends  and  corners 
are  hotter,  strains  are  set  up  in  the  piece,  and  it  is  very 
liable  to  crack  when  hardened.  This  also  applies  to  a 
piece  of  any  shape.  While  it  is  extremely  necessary 
that  the  operator  observe  the  greatest  possible  care  in 
regard  to  the  quantity  of  heat  given  steel,  yet  it  does 
not  harm  steel  as  much  to  heat  it  a  trifle  too  hot  as  it 
does  to  heat  it  unevenly,  for  while  the  higher  heat  un- 
fits it  for  doing  the  maximum  amount  of  work  possible, 
the  uneven  heat  is  very  liable  to  cause  it  to  crack  when 
hardened. 

A  piece  of  steel  should  not  be  heated  faster  than  is 
possible  to  maintain  a  uniform  heat.     By  this  is  meant 

60 


The  condition  of  the  grain  of  steel. 

the  heating  should  not  be  forced  so  that  the  outside  is 
red  hot  while  the  center  is  black  because  in  all  prob- 
ability the  furnace  would  be  so  hot  that  the  outside  of 
the  article  would  keep  growing  hotter  while  the  center 
was  getting  to  the  desired  heat.  The  result  would  be 
an  uneven  heat.  Neither  should  a  piece  of  steel  be 
any  longer  in  heating  than  is  necessary,  because  after  it 
is  red  hot,  it  will,  if  exposed  to  the  action  of  the  air, 
become  somewhat  decarbonized  on  the  surface,  thus 
materially  affecting  the  steel.  Tool  steel  should  be 
heated  as  fast  as  it  will  take  heat,  and  no  faster.  A 
piece  should  not  be  forced  by  heating  the  furnace  to  a 
temperature  that  will  affect  the  surface  while  the  heat 
is  equalizing.  Steel  should  never  be  heated  too  hot, 
and  allowed  to  cool  to  what  is  considered  the  proper 
heat,  and  then  hardened,  as  the  grain  will  be  as  coarse 
as  if  dipped  at  the  high  heat. 

The  grain  of  steel  remains  in  the  condition  the 
highest  heat  received  leaves  it,  until  it  is  reheated, 
when  it  is  adjusted  to  that  heat.  The  condition  of  the 
grain  of  the  steel  is  an  unvarying  guide  as  to  the 
amount  of  heat  it  received  the  last  time  it  was  heated. 
For  instance,  a  piece  of  steel  is  heated  to  the  tempera- 
ture of  the  piece  marked  4  Fig.  2  2  in  our  experiment. 
Now,  take  one  of  the  broken  pieces  and  reheat  it  to  a 
temperature  given  the  piece  marked  2,  which  was  the 
refining  heat.  Break  this  piece.  An  examination  will 
reveal  the  fact  that  the  grain  has  the  same  structure  as 
the  piece  marked  2,  thus  proving  that  the  grain  of  steel 
conforms  to  the  last  heat  given  it.  This  does  not 
necessarily  prove  that  a  piece  of  steel  is  capable  of 
doing  the  amount  of  work  after  it  has  been  heated 
hotter  than  it  should  have  been,  and  then  reheated  to  a 

6x 


Harden  on  a  "rising  heat." 

lower  heat,  thus  closing  the  pores ;  but  it  is  better  than 
if  in  the  condition  the  high  heat  would  leave  it. 

Steel  should  always  be  hardened  on  what  is  known 
as  a  ''rising"  heat,  never  on  a  ''falling"  heat,  is  the 
advice  an  old  hardener  gave  the  writer  when  a  boy, 
learning  his  trade,  and  he  has  found  it  true.  It  also 
agrees  with  the  advice  of  most  writers  on  this  subject. 
It  is  quite  necessary,  in  order  to  get  uniform  results,  to 
move  the  articles  around  in  the  furnace  and  turn  them 
over  occasionally.  When  round  (cylindrical)  pieces  of 
steel,  having  no  teeth,  projections,  or  other  irregulari- 
ties on  its  surface,  are  being  heated  for  hardening,  it 
is  necessary  to  turn  them  occasionally,  as,  if  left  in  one 
position  without  turning,  until  it  is  red  hot,  no  matter 
how  uniform  the  heat  may  be,  it  will,  in  all  probability, 
have  a  soft  line  the  entire  length  of  the  top  side  as  it 
lay  in  the  fire.  It  will  also  be  found  by  experiment 
that  round  pieces  are  more  liable  to  crack  from  uneven 
heating  than  pieces  of  almost  any  other  shape ;  neither 
will  they  safely  stand  as  high  a  degree  of  heat  as  some 
pieces,  on  account  of  their  shape,  which  makes  them 
offer  greater  resistance  to  a  change  of  form. 

If  possible,  when  heating  articles  having  heavy 
and  light  sections  adjoining  each  other,  as  shown  in 
Fig.  23,  heat  the  heavy  portion  first,  then  the  lighter 
one;  but  if  this  is  not  possible,  have  a  slow  fire,  in 
order  that  the  light  part  may  not  be  overheated  before 
the  heavy  one  is  to  the  required  heat.  The  muffle 
furnace  furnishes  a  very  satisfactory  method  of  heating 
steel,  because  the  products  of  combustion  cannot  come 
in  contact  with  the  steel,  and  oxidation  from  the  action 
of  the  air  is  done  away  with  or  reduced  to  the  minimum. 
If  it  is  not  possible  to  use  a  furnace  of  this  description, 

6z 


When  coals  should  not  be  used. 

very  good  results  may  be  obtained  by  enclosing  the 
article  in  a  piece  of  pipe  or  tube  and  beating  in  an  open 
fire,  because  in  this  case  the  steel  is  not  exposed  to  the 
action  of  the  fire.  It  is  necessary  to  turn  the  work 
over  occasionally  in  order  to  get  a  uniform  heat. 

It  is  never  advisable  to  use  any  kind  of  fire  where 

the  air  from  the  blast 


Tlie  D-irry  Collard  Co. 

Figure  23.     A  piece  for  a  slow  fire. 


can  strike  the  piece  be- 
ing heated,  or  it  will 
crack  in  innumerable 
places.  The  steel  will 
look  as  though  it  were 
full  of  hairs.  For  this 
reason,  if  obliged  to  use 
a  blacksmith's  forge,  build  a  fire  high  enough  to  do 
away  with  any  tendency  of  this  trouble.  A  fire  of  old 
coals  should  not  be  used  if  the  article  to  be  heated  is  of 
any  size,  as  the  goodness  is  burned  out  of  the  coal, 
and  it  will  be  found  necessary  to  use  a  strong  blast  in 
order  to  have  a  fire  hot  enough  to  heat  the  piece. 
As  a  consequence,  the  air  strikes  the  piece  with  the 
result  mentioned. 

Steel  should  not  be  heated  in  a  manner  that  leaves 
one  side  exposed  to  the  air,  or  the  exposed  side  will 
become  oxidized  to  a  considerable  extent,  and  as  the 
piece  is  turned  in  the  fire  the  whole  surface  becomes 
oxidized  and  resembles  a  piece  of  burnt  steel.  The 
surface  is  not  of  any  use,  as  the  carbon  is  burned  out, 
and  it  cannot  be  hardened.  Some  makes  of  steel  give 
off  their  surface  carbon  very  readily  if  exposed  to  the 
air  when  red  hot.  If  a  tool  made  from  one  of  these 
steels  be  heated  in  a  manner  that  allows  the  air  to  come 
in  contact  with  it,  the  outside  becomes  decarbonized. 


63 


The  indifference  of  some  hardeners. 

and  consequently  is  soft,  while  the  metal  undemeatli 
the  surface  is  extremely  hard.  Now,  this  might  not  be 
harmful  in  the  case  of  a  tool  whose  outer  surface  was 
to  be  ground  away,  but  if  the  surface  of  a  tap,  formed 
mill  or  similar  tool  becomes  decarbonized,  it  is  practi- 
cally useless.  Now,  if  these  same  tools  had  been 
heated  in  a  muffle  furnace  or  in  a  piece  of  pipe  in  the 
open  fire,  removed  from  the  action  of  the  fire  and  the 
air,  the  result  would  have  been  that  the  tool  would 
have  given  excellent  satisfaction.  While  all  makes  of 
steel  are  not  so  sensitive  to  the  action  of  the  fire  and 
air  when  they  are  red  hot,  yet  any  steel  gives  better 
results  if  it  is  removed  from  their  action  while  in  this 
condition. 

A  man  experienced  in  the  effects  of  heat  on  steel 
is  surprised  at  the  apparent  indifference  of  some  hard- 
eners when  heating  steel.  A  tool  hardened  properly 
and  tested  for  strength  in  a  testing  machine  will  be 
found  very  much  stronger  than  if  heated  a  trifle  hotter. 
When  we  consider  that  hardness,  toughness  and  close- 
ness of  grain  are  the  qualities  desired  in  a  cutting  tool, 
we  realize  that  there  is  nothing  gained  by  heating  tool 
steel  above  the  refining  heat  for  most  work.  Steel 
quenched  at  this  heat  is  very  hard,  tough,  and  the  grain 
is  the  finest  possible.  Now,  every  degree  of  heat  which 
it  receives  above  this  point  unfits  it  for  doing  the 
maximum  amount  of  work  possible,  because  it  causes 
the  steel  to  be  brittle  and  makes  the  grain  coarse. 

The  writer  has  made  exhaustive  experiments  in 
regard  to  the  effects  of  heat  on  the  strength  of  steel, 
and  assures  the  reader  that  a  piece  of  steel  hardened  at 
the  refining  heat  requires  a  much  greater  force  to 
break  it  than  one  heated  to  a  full  red.     Knowing  this, 

64 


Reheating  to  remove  strains. 

the  reader  can  judge  how  much  heavier  cuts  can  be 
taken  with  a  tool  properly  heated  than  with  one  heated 
too  hot,  as  the  steel  is  made  brittle,  and  in  this  condi- 
tion is  more  liable  to  chip  or  flake  off  under  pressure. 
The  grain  being  coarse  does  not  present  a  dense  body, 
but  the  internal  structure  has  a  honeycomb  appear- 
ance ;  consequently  when  pressure  is  applied  the  surface 
caves  in,  because  it  does  not  have  the  backing  it  would 
if  the  grain  were  compact. 


Reheating  to  Remove  Strains. 

As  steel  heated  red-hot  and  cooled  quickly  con- 
tracts, and  as  the  outer  surface  hardens  and  becomes 
rigid  before  the  interior  of  the  piece  has  ceased  con- 
tracting and  altering  its  form  and  the  position  of  its 
molecules,  the  molecules  that  make  up  the  interior  of 
the  piece  cannot  assume  the  exact  positions  they 
should ;  consequently,  strains  are  set  up.  Now,  if  the 
outer  portion  of  the  article  is  sufficiently  strong  to 
resist  the  tendency  of  the  interior  of  the  piece  to  alter 
its  form,  it  may  not  crack  or  it  may  resist  the  strain 
for  a  considerable  length  of  time.  But  for  some  cause 
a  certain  portion  of  the  exterior  of  the  piece  becomes 
weakened,  or  the  conditions  are  such  that  the  outside 
can  not  longer  resist  the  internal  strain,  and  the  piece 
is  cracked,  or  it  may  burst.  Many  times  large,  heavy 
pieces  of  steel  will  burst  with  a  report  as  loud  as  a  gun, 
and  pieces  of  the  steel  will  be  carried  for  some  distance 
by  the  force  exerted. 

Now,  in  order  to  avoid  this  tendency,  it  is  neces- 
65 


Pliability  of  hardened  steel. 

sary  to  reheat  the  piece  as  soon  as  it  is  taken  from  the 
hardening  bath,  to  a  temperature  that  allows  the  vari- 
ous portions  of  the  piece  to  conform  to  one  another. 
A  piece  of  hardened  steel  becomes  pliable  to  a  degree 
when  heated,  the  amount  of  pliability  depending  on 
the  temperature  to  which  the  piece  is  heated.  This  is 
illustrated  elsewhere  in  the  case  of  articles  crooked  in 
hardening,  which  are  straightened  after  heating  to  a 
certain  temperature.  After  cooling  they  remain  the 
shape  given,  but  were  we  to  attempt  to  spring  them  as 
much  when  cold,  they  would  certainly  break. 

It  is  advisable,  after  taking  a  piece  of  hardened 
steel  from  the  bath,  to  hold  it  over  a  fire  or  in  some  man- 
ner subject  it  to  heat,  in  order  that  it  may  become 
pliable  enough  to  remove  the  tendency  to  crack  from 
internal  strains. 

The  method  pursued  in  removing  the  strains 
varies.  If  an  open  fire  is  at  hand,  the  piece  may  be 
held  over  this  until  heated  to  the  proper  temperature. 
It  should  be  constantly  turned,  in  order  to  insure  uni- 
form results.  When  pieces  are  hardened  in  large 
quantities,  this  is  a  very  expensive  practice.  In  such 
cases,  it  is  advisable  to  have  a  tank  of  oil,  which  is 
kept  at  the  desired  temperature,  this  being  gauged  by 
means  of  a  thermometer. 

A  very  satisfactory  method,  and  one  used  by  the 
writer  for  many  years,  consists  in  using  a  tank  of 
water,  the  contents  of  which  are  kept  at  the  boiling 
point  (212°).  When  a  piece  of  hardened  steel  is 
removed  from  the  bath,  it  is  immediately  dropped  in 
the  boiling  water.  The  tank  has  a  catch  pan  to  receive 
the  work,  as  shown  in  Fig.  24.  A  steam  pipe  is  con- 
nected with  the  tank  in  order  to  keep  the  water  at  the 

66 


The  removal  of  internal  strains. 


Perforated  Catch  Pan 


\'<'«'<'<'<'<'<'<'<'W<'<'<'/^/W<'<'('<'/^<l 


desired  temperature.      It  is,    of  course,   necessary  to 
provide  an  overflow  pipe,  as  represented. 

When  it  is  not  considered  advisable  to  procure  a 
tank,  as  represented,  a  kettle  of  water  may  be  placed 
over  a  fire  and  brought  to  the  boiling  point  and  used 
as  described. 

When  it  is  thought  to  be  advisable  to  remove  the 

tendency  to  crack 
from  internal 
strains  and  draw 
the  temper  at  the 
same  time,  it  may 
be  done  by  heating 
a  kettle  of  oil  to 
the  desired  tem- 
perature, gauging 
the  heat  by  a  ther- 
mometer.  The 
pieces,  as  they  are 
taken  from  the 
hardening  bath, 
may  be  dropped  in 
this  and  left  long 
enough  to  insure 
uniform  heating. 
Should  it  be  considered  advisable  to  heat  articles 
of  irregular  shape,  having  heavy  and  light  portions 
adjoining  each  other,  it  would  not  be  advisable  to  sud- 
denly immerse  them  in  liquid  heated  to  300°,  400°  or  500° 
Fahr. ,  as  the  unequal  expansion  might  cause  the  pieces 
to  crack  where  the  heavy  and  light  portions  joined. 
In  such  cases  it  is  sometimes  considered  advisable  to 
place  them  in  a  kettle  of  boiling  water  first,  removing 

67 


\^^ 


Th«  Derry  Collard  Co. 

Figure  24.     Tank  of  boiling  water 
for  removing  internal  strains. 


Forging  troubles. 

them  from  time  to  time  and  placing  in  the  kettle  of 
oil,  heated  to  the  temperature  to  which  the  pieces  must 
be  heated  in  drawing  temper;  or  two  kettles  of  oil, 
heated  to  different  temperatures,  are  sometimes  used, 
the  first  being  kept  at  250°  or  as  as  near  that  as  possi- 
ble, the  other  being  the  desired  temperature.  When 
the  pieces  are  removed  from  the  first  kettle  and  placed 
in  the  second,  it,  of  course,  reduces  the  temperature  of 
the  oil,  but  it  gradually  rises  to  the  desired  point  when 
the  articles  are  removed. 


Forging. 


CO 

It  is  not  the  writer's  intention  to  devote  much 
space  to  explanation  of  the  method  in  which  steel 
should  be  forged  for  the  various  cutting  tools.  In 
order  to  do  the  subject  justice,  it  would  be  necessary 
to  devote  more  space  than  can  be  spared,  but  the  forg- 
ing and  hardening  of  a  tool  are  so  closely  identified,  it 
seems  necessary  to  briefly  consider  the  subject. 

Many  tools  are  rendered  unfit  for  use  by  the  treat- 
ment they  receive  in  the  forge  shop,  and  as  it  is  the 
custom  in  many  shops  to  have  the  forging  done  by  one 
man,  and  the  hardening  by  another,  a  great  amount  of 
trouble  is  experienced,  because  each  tries  to  lay  any 
trouble  that  comes  from  the  hardened  product  to  the 
other. 

Heating  is  the  most  important  of  the  operations  to 
which  it  is  necessary  to  subject  steel,  whether  it  be  for 
forging,  annealing  or  hardening. 

6S 


Superiority  of  hammered  steel. 

Unless  steel  is  uniformly  heated  throughout,  vio- 
lent strains  are  set  up;  when  the  piece  is  hardened 
these  manifest  themselves.  If  the  steel  is  not  heated 
uniformly  throughout  the  mass,  it  cannot  flow  evenly 
under  the  blows  of  the  hammer,  consequently  the  grain 
is  not  closed  in  a  uniform  manner. 

While  it  is  necessary,  in  order  to  get  satisfactory  , 
results,  to  heat  steel  hot  enough  to  make  it  plastic,  in 
order  that  it  may  be  hammered  to  shape,  care  should 
be  exercised  that  it  is  not  overheated,  or  the  grain  will 
be  opened  to  an  extent  that  it  can  not  be  closed  by  any 
means  at  hand  in  the  ordinary  forge  shop. 

If  a  large  piece  of  steel  requiring  considerable 
change  in  size  is  to  be  forged,  and  means  are  at  hand 
to  forge  it  with  heavy  blows,  it  can  safely  be  given  a 
higher  heat  than  a  smaller  article  which  does  not  require 
much  change  of  size  or  form. 

If  tool  steel  is  hammered  carefully,  with  heavy 
blows  while  it  is  the  hottest,  and  then  with  lighter, 
more  rapid  blows  as  it  cools,  the  grain  will  be  closed 
and  become  very  fine. 

When  the  temperature  is  reduced  to  a  low  red, 
care  should  be  exercised,  for  when  traces  of  black  begin 
to  show  through  the  red,  it  is  dangerous  to  then  give  it 
any  heavy  blows,  as  they  would  crush  the  grain. 

By  actual  test  it  has  been  proven  time  and  again 
that  steel,  which  has  been  properly  hammered,  is  super- 
ior to  the  same  steel  as  it  comes  from  the  steel  mill, 
but  unless  the  work  is  done  by  an  intelligent  smith, 
who  understands  the  effect  of  heat  on  the  structure  of 
steel,  the  forging  will  have  the  opposite  effect  to  the 
one  desired. 

Many  steel  manufacturers  advocate  the  purchase 
69 


"Hammer  refined"  steel. 

of  steel  in  bars  of  the  desired  size,  and  do  not  advise 
forging,  claiming  best  results  if  tbe  article  is  machined 
to  size  and  shape.  The  reason  for  this  is,  that  there 
are  many  careless,  ignorant  workers  of  steel  in  the 
various  blacksmith  shops — men  who  either  do  not  know 
the  effects  of  improper  methods  of  heating  and  ham- 
mering, or  knowing,  do  not  care.  As  a  consequence, 
a  great  quantity  of  steel  is  annually  rendered  unfit  for 
doing  the  work  it  might  do  were  it  treated  properly. 

For  this  reason  it  is  advisable  to  machine  a  piece 
of  steel  to  shape,  rather  than  to  have  it  forged  by  any 
but  a  skillful  smith.  Yet  the  fact  remains  that  a  piece 
of  steel  heated  and  hammered  properly  will  do  more 
work  than  a  tool  of  the  same  description  cut  from  the 
same  bar  and  machined  to  shape,  even  if  it  is  hardened 
in  exactly  the  same  manner. 

A  piece  of  steel  properly  forged  is  known  by  tool 
makers  as  * 'hammer  refined"  steel,  and  is  highly  valued 
by  them  for  tools  which  are  expected  to  do  extra  hard 
work.  Tool  steel  is  furnished  in  bars,  blanks  or  forg- 
ings  of  almost  any  desired  shape. 

The  smith  should  bear  in  mind  that  heats  which 
are  too  high  open  the  grain,  thereby  weakening  the 
steel  and  making  it  incapable  of  doing  the  largest 
amount  of  work  possible.  If  steel  is  hammered  when 
too  cold,  the  grain  is  crushed,  causing  it  to  crack  when 
hardened ;  or  if  it  does  not  crack,  the  cutting  edges  will 
flake  off  when  in  use.  If  the  steel  is  unevenly  heated, 
that  is,  the  outside  heated  hotter  than  the  inside,  the 
outside  portion  being  softer  will  respond  to  the  action 
of  the  hammer  more  readily  than  the  less  plastic  in- 
terior, and  the  outer  portion  will  be  torn  apart. 

T-^o  often  it  happens  that  when  the  smith  is  rushed 

70 


The  object  of  annealing  steel. 

with  work  he  will  attempt  to  heat  a  large  bar  of  iron 
for  forging,  and  while  that  is  heating,  will  try  to  forge 
or  harden  tools  someone  is  waiting  for.  The  spirit  of 
willingness  to  accommodate  is  commendable,  but  a 
decided  lack  of  judgment  is  noticeable,  because  a  fire 
suitable  for  heating  a  piece  of  iron  to  a  forging  heat 
is  in  no  ways  adapted  to  heating  a  tool  either  for  forg- 
ing or  hardening. 

Then  again,  if  the  smith  is  heating  iron  to  its 
proper  forging  heat,  his  eyes  are  in  no  condition  to 
properly  discern  the  correct  heat  to  give  a  piece  of  tool 
steel. 


Annealing, 


CO 

According  to  the  generally  accepted  definition  of 
the  term,  the  object  of  annealing  steel  is  to  soften  it  in 
order  that  it  may  be  machined  at  the  minimum  cost  of 
labor  and  tools. 

The  method  pursued  in  annealing  steel  depends,  as 
a  rule,  on  the  facilities  which  the  shop  possesses  for 
doing  this  class  of  work.  A  piece  may  be  softened 
somewhat  by  heating  red-hot  and  laying  it  to  one  side 
to  cool  in  the  air,  provided  it  is  not  placed  on  any  sub- 
stance that  will  chill  it.  Neither  should  it  be  placed 
where  any  current  of  air  can  strike  it,  or  it  will  cool 
too  quickly  to  become  soft.  In  fact,  it  would  very 
likely  be  harder  than  if  worked  without  attempting  to 
anneal  it. 

The  young  hardener  should    understand   that   a 

71 


How  annealing  is  best  done, 

piece  of  steel  is  hardened  by  heating  red-hot  and  cool- 
ing quickly ;  the  more  rapid  the  process  of  cooling,  the 
harder  the  steel  will  be.  Annealing  has  the  opposite 
effect.  Steel  is  annealed  by  heating  red-hot  and  cool- 
ing slowly ;  the  greater  the  amount  of  time  consumed 
in  the  cooling  operation,  the  softer  the  steel  will  be, 
everything  else  being  equal.  Now,  it  is  evident  that, 
if  a  piece  of  steel  be  heated  to  a  red  and  placed  on  an 
anvil  or  other  piece  of  cold  metal  or  thrown  on  the 
floor,  the  portion  laying  on  the  cold  substance  will 
chill  and  the  process  of  hardening,  rather  than  anneal- 
ing, will  be  carried  on. 

The  same  is  true  if  a  piece  is  placed  where  a  cur- 
rent of  air  can  strike  it,  even  if  it  is  warm  air,  as  it  will 
be  cooler  than  the  steel  and  the  heat  in  the  steel  will  be 
taken  up  by  the  air.  Thus,  the  operation  will  be  the 
opposite  of  the  one  desired. 

It  is  the  custom  in  many  shops  to  anneal  steel  by 
heating  and  putting  it  in  a  box  of  ashes  or  lime.  Now, 
this  may  be  advisable,  or  it  may  not  be,  according  to  the 
condition  of  the  contents  of  the  annealing  box.  If  the 
room  in  which  the  box  is  kept  is  damp,  the  ashes  or 
lime,  especially  the  lime,  will  absorb  enough  moisture 
to  chill  the  piece  of  red-hot  steel,  particularly  if  it  be 
small  or  thin.  So  we  have  again  a  piece  of  steel 
hardened  to  a  degree,  instead  of  annealed.  When  steel 
is  to  be  annealed  by  this  process,  it  is  advisable  to  heat 
a  piece  of  iron  or  scrap  steel  and  bury  it  in  the  ashes 
or  lime,  leaving  it  there  until  the  piece  to  be  annealed 
is  properly  heated,  when  it  may  be  removed,  and  the 
piece  to  be  annealed  put  in  its  place.  The  ashes  or 
lime  being  heated,  and  every  trace  of  moisture  removed, 
the  process  of  cooling  will  be  slow  and  the  results 

72 


Methods  of  annealing. 

satisfactory.  A  box  of  lime  furnishes  an  excellent 
method  of  annealing  steel,  if  the  precaution  mentioned 
is  observed. 

A  very  satisfactory  method  of  annealing,  which  has 
been  used  by  the  writer  many  times  where  there  was 
only  one  or  two  pieces  to  anneal  at  a  time,  consists  in 
taking  an  iron  box,  putting  two  or  three  inches  of  ashes 
in  the  bottom  and  laying  a  piece  of  board  a  trifle  larger 
than   the  work   on  them.     Heat   the  pieces  to  be  an- 
nealed to  the  proper 
degree,  lay  them  on 
the  board,   lay  an- 
other piece  of  board 
on  top  of  them,  and 
fill    the    box    with 
ashes,   as  shown  in 
Fig.  25.    The  pieces 
of    board    will 
smoulder  and  keep 
the  steel  hot  for  a 
long  time.   The  pro- 
cess of  cooling  will 
be  very  slow. 
There  is  a  method  of  annealing  practiced  in  some 
shops  which,  while  it  has  many  advocates,  cannot  be 
recommended  by  the  writer,  except  as  a  means  of  an- 
nealing a  piece  of  steel  that  is  wanted  right  away.     It 
is  known  as  cold  water  annealing.     This  method  has 
advocates  among  old  hardeners,   some  of  whom  get 
excellent  results;  but  as  a  method  of  annealing  to  be 
practiced  by  one  who  is  not  thoroughly   familiar  with 
the  action  of  fire  and  water  on   tool  steel,  its  use  is 
hardly  to  be  advocated.     The  steel  is  heated  to  a  red 


^s 

=  =  =  — 

fLTLnj;;; 

Work 

-= — !~-^ 

^=^^^ 

'^— — ' — —-T- 

Ib=^=I:=^=^fj 

1 

Figure  25. 

An  iron  box  filled  with  ashes  for  annealing 
between  boards. 


73 


Annealing  in  gas  furnace. 

and  allowed  to  cool  in  the  air  where  no  current  of  air 
can  strike  it,  held  in  a  dark  place,  and  when  every 
trace  of  red  has  disappeared,  plunged  in  water  and  left 
until  cold.  The  steel  will  be  softer  if  plunged  into 
soapy  water  or  oil. 

This  answers  in  an  emergency,  but  on  account  of 
the  ends  cooling  faster  than  the  center  and  the  smaller 
portions  cooling  more  rapidly  than  the  larger  ones,  it  is 
apparent  that  the  piece  of  steel  must  be  of  an  uneven 
temperature  throughout  when  cooled. 

The  method  practiced  in  many  shops  of  heating  a 
piece  of  steel  in  a  furnace  to  the  proper  annealing  heat, 
using  gas,  oil  or  gasoline  as  fuel,  then  shutting  off  the 
supply  and  allowing  the  work  to  cool  down  with  the 
furnace,  is  attended  with  varying  results.  While  many 
mechanics  advocate  this  method  and  claim  excellent 
results,  and  it  has  been  used  by  the  writer  to  his  entire 
satisfaction,  yet  several  cases  have  come  to  his  notice 
of  late  where  parties  had  annealed  this  way  with  re- 
sults that  were  far  from  satisfactory.  Investigation 
showed  that  in  heating  the  steel  the  furnace  had  been 
forced  in  order  to  heat  the  piece  quickly,  and  as  the 
steel  was  heated  by  radiation  it  was  necessary  that  the 
walls  of  the  furnace  should  be  hotter  than  the  piece  of 
steel  being  heated. 

When  the  steel  had  apparently  reached  the  proper 
heat,  the  supply  of  fuel  was  shut  off,  but  the  inside 
walls  of  the  furnace,  being  much  hotter  than  the  work, 
imparted  heat  to  the  steel  after  the  fire  was  put  out, 
with  the  result  that  the  steel  was  overheated  and 
injured,  and  in  some  cases  entirely  unfitted  for  the  use 
it  was  intended  for.  A  steel  maker  of  national  reputa- 
tion says  that  **many  thousand  dollars'  worth  of  steel  are 

74 


Annealing  in  iron  boxes. 

ruined  annually  in  this  way,  and  it  is  in  every  way  about 
the  worst  method  of  annealing  that  was  ever  devised.'' 

Knowing  the  vast  amount  of  trouble  caused  by 
attempts  of  various  parties  to  use  this  method,  the 
writer  feels  it  his  duty  to  condemn  a  method  he  has 
used  successfully  under  favorable  circumstances,  be- 
cause all  mechanics  are  not  so  favorably  situated. 
They  do  not  use  the  same  care  in  heating  steel,  especi- 
ally when  it  is  nearly  to  the  proper  temperature,  but 
insist  on  forcing  it,  not  only  to  the  detriment  of  the 
edges  and  comers,  which  are  bound  to  heat  faster  than 
the  center.  In  this  way  the  whole  piece  is  ruined  or 
injured,  because  the  furnace  is  hotter  than  the  steel, 
and  when  the  fire  was  extinguished,  the  furnace  was 
closed  and  there  was  no  means  of  looking  in  to  deter- 
mine the  amount  of  heat  the  steel  was  receiving,  but 
the  results  showed  it  had  been  heated  too  much  for  its 
good. 

Now,  if  a  comparatively  small  furnace  is  used,  or 
one  having  light  walls,  which  will  not  hold  the  heat  for 
a  very  great  length  of  time,  the  danger  of  over-heating 
by  radiation  after  the  fire  is  extinguished  is  reduced  to 
the  minimum.  But  on  the  contrary,  if  the  furnace  has 
heavy  walls  of  masonry,  capable  of  retaining  the 
excessive  heat  for  a  considerable  length  of  time,  the 
liability  of  overheating  is  very  great. 

A  method  of  annealing  that  gives  universal  satis- 
faction when  properly  done,  and  is  used  in  many  shops, 
consists  in  packing  the  steel  in  iron  boxes  and  filling 
the  spaces  between  the  pieces  of  steel  with  powdered 
charcoal.  It  is  necessary  when  annealing  by  this 
method  to  place  one  or  two  inches  of  charcoal  in  the 
bottom  of  the  box  before  putting  in  any  steel.     Do  not 

75 


Box  method  of  annealing. 

allow  the  pieces  of  steel  to  come  within  one-half  inch 
of  each  other  in  the  box,  or  within  one  inch  of  the  box 
at  any  point. 

When  nearly  full,  fill  the  balance  of  the  space  with 
charcoal,  put  on  the  cover  and  seal  the  edges  with  fire- 
clay. The  reason  for  keeping  the  steel  from  coming 
into  contact  with  the  box  is  that  the  iron,  especially 


The  Derry  Collard  Co. 


nzzi  nz2  L 


IZZ3  czzi  i:=zi 
[z:]  czi  cm 


[IZI  cm  LU 


Myy/My///^//////////^^^^ 


Figure  26.      Iron  box  for  annealing. 


cast  iron,  has  a  great  affinity  for  carbon,  and  will, 
when  they  are  both  red  hot,  extract  it  from  the  steel, 
leaving  the  latter  somewhat  decarbonized  at  the  point 
of  contact. 

In  order  to  be  able  to  determine  when  the  contents 
of  the  box  are  heated  to  the  proper  degree,  several  ^ 
inch  holes  should  be  drilled  through  the  center  of  the 
cover  and  a  -^  wire  run  down  through  each  of  these 

76 


Process  of  annealing  in  boxes. 

to  the  bottom  of  the  box,  as  shown  in  the  sectional 
view,  Fig-.  26. 

When  the  box  has  been  in  the  fire  long  enough, 
according  to  the  judgment  of  the  operator,  to  heat 
through,  draw  one  of  these  wires  by  means  of  a  pair  of 
long-handled  tongs,  or  by  a  pair  of  ordinary  length, 
slipping  a  piece  of  gas  pipe  on  each  leg  to  give  the  re- 
quired length.  If  the  wire  drawn  shows  hot  the  entire 
length,  the  operator  may  rest  assured  that  the  steel  is 
of  the  same  temperature,  because  the  wire  v/as  run 
down  between  the  pieces  at  the  center  of  the  box.  If 
the  wire  did  not  show  red-hot,  wait  a  while  and  draw 
another.  When  a  wire  is  drawn  that  shows  the  proper 
degree  of  heat,  the  box  should  be  left  long  enough  to 
insure  its  being  heated  uniformily  throughout,  then  the 
fire  may  be  extinguished.  If  the  walls  of  the  furnace 
are  much  hotter  than  the  boxes,  the  door  may  be  left 
open  until  they  are  somewhat  cool.  If  the  furnace 
shows  a  disposition  to  heat  the  boxes  too  hot  with  the 
door  open,  they  may  be  removed  for  a  few  minutes 
until  the  furnace  is  somewhat  cooler,  when  the  boxes 
may  be  returned  to  the  furnace,  the  door  closed  and 
the  work  allowed  to  cool  slowly. 

A  method  that  insures  excellent  results  is  to  plan, 
if  possible,  to  empty  one  furnace  of  work  to  be  hard- 
ened some  little  time  before  the  work  being  annealed 
is  sufficiently  heated.  Keep  the  first  furnace  closed  to 
retain  the  heat  as  much  as  possible,  so  that  it  will  pass 
the  stage  where  it  is  liable  to  overheat  the  articles,  and 
it  will  commence  to  cool  down  somewhat.  When  the 
work  being  heated  for  annealing  has  been  subjected  to 
the  heat  a  sufficient  length  of  time,  the  boxes  may  be 
removed    from    the  furnace  they  were  heated  in  and 

77 


Blocking  out  work  for  annealing. 


Figure  27. 


An  irregular  milling 
cutter. 


placed  in  the  first  furnace.     All  danger  of  heating  too 
hot  from  radiation  is  done  away  with.     This  method 
cannot,   of  course,   be  prac- 
ticed  if    there    is    but    one 
furnace. 

While  it  is  generally  un- 
derstood that  the  object  of 
annealing  steel  is  to  make  it 
soft  enough  to  work  to  ad- 
vantage, yet  from  the  hard- 
ener's standpoint  annealing 
has  another  and  more  import- 
ant office  than  simply  to 
make  steel  workable. 

A  piece  of  steel  as  it  comes  from  the  steel  mill  or 
forge  shop  is  very  apt  to  show  a  difference  of  grain  in 
various  parts  of  the  piece,  due  to  uneven  heating  and 
an  unequal  closing  of  the  pores  in  the  process  of  rolling 
or  hammering ;  consequently 
there  exists  in  the  piece  internal 
strains.  In  order  to  overcome 
the  effect  of  these  internal 
strains,  which  must  manifest 
themselves  when  the  steel  is 
hardened,  the  work  should  be 
blocked  out  somewhere  near  the 
shape  and  annealed.  If  the 
piece  is  a  milling  machine  cut- 
ter, punch  press  die,  or  similar 
tool,  having  one  or  more  holes 
through  it,  the  holes  should  be  made  somewhat  smaller 
than  finish  size  before  annealing  to  remove  strains.  If 
it  is  a  milling  machine  cutter  of  irregular  contour,  as 

78 


Figure  a8.      Irregular  milling 

cutter  blocked  out  for 

annealing. 


How  to  straighten  work  after  springing. 

shown  in  Fig.  27,  it  should  be  blocked  out  as  repre- 
sented in  Fig.  28.  The  benefit  gained  in  pursuing  this 
course  is  that  it  is  heated  for  annealing  under  as 
nearly  as  possible  the  same  conditions,  so  far  as  shape 
is  concerned,  as  when  heated  for  hardening;  conse- 
quently the  tendency  to  change  shape  will  be  overcome 
in  the  annealing. 

Long  pieces  of  steel  that  are  to  be  hardened  will 
give  much  better  results  if  roughed  out — that  is,  all 
scale  and  outside  surface  removed  by  planing  or  turn- 
ing— then  thoroughly  annealed.  Should  the  piece 
spring  when  annealing  do  not  straighten  when  cold,  as 
it  is  almost  sure  to  spring  when  hardened.  If  it  is  not 
sufficiently  large  to  turn  out  without  straightening,  it 
should  be  heated  red-hot  and  straightened.  The  hard- 
ener is  blamed  many  times  because  a  costly  reamer  or 
broach  or  similar  tool  is  crooked  in  hardening,  when  in 
reality  the  blame  rests  with  the  man  who  turned  or 
planed  it  to  size. 

After  it  was  annealed  he  tested  it  in  the  lathe,  and 
finding  it  running  out  somewhat  he  takes  it  to  an  iron 
block  or  an  anvil,  and  commences  to  hammer.  He  fin- 
ally gets  it  fairly  straight,  and  feels  quite  proud  of  his 
job.  He  doesn't  like  to  see  a  man  machine  a  piece  of 
steel  that  is  crooked  even  if  it  will  finish  out,  when  a 
few  strokes  of  a  hammer  will  fix  it  all  right. 

He  has,  by  means  of  hammering,  set  up  a  system 
of  internal  strains  much  more  serious  than  the  ones 
removed  by  the  process  of  annealing.  He  commences 
to  machine  the  piece.  Every  time  he  goes  below  the 
effects  of  a  hammer  mark,  the  particles  of  the  piece  of 
steel  **goes  "  or  moves  in  some  direction  at  this  point, 
and  it  is  necessary  to  repeat  the  operation  of  hammer 

79 


Shifting  the  blame. 

persuasion  again,  with  the  effect  that  by  the  time  the 
article  is  ready  to  harden,  it  is  in  no  condition  to  be 
hardened.  It  is  either  crooked  in  all  directions,  or  it 
is  only  waiting  for  the  fire  to  relieve  it  and  allow  it  to 
go  where  it  will.  When  the  hardener  gets  through 
with  it,  it  looks  like  a  cow's  horn,  and  of  course  the 
hardener  is  blamed. 

If  he  happens  to  be  a  man  without  any  machine 
shop  experience,  or  does  not  understand  the  nature  and 
peculiarities  of  steel,  he  does  not  know  where  to  place 
the  blame,  and  perhaps  it  wouldn't  do  any  good  if  he 
did. 

He,  of  course,  isn't  going  to  shoulder  it,  so  the 
fault  is  laid  to  the  steel,  and,  in  consequence,  if  the 
trouble  continues,  another  make  of  steel  is  bought  be- 
cause the  man  in  charge  does  not  know  or  cannot  spend 
time  to  locate  the  trouble.  It  cannot  be  the  fault  of 
the  man  in  the  shop,  they  say ;  it  must  be  the  steel ;  or 
they  decide  it  must  be  the  hardener,  because  some 
other  concern  with  whom  they  are  acquainted  use  this 
same  steel  and  have  no  trouble,  so  the  hardener  has  to 
stand  the  blame. 

A  successful  business  man  is  quoted  as  saying: 
**If  I  were  to  drive  a  mule  team,  I  would  study  the 
nature  of  mules."  A  man  to  be  a  successful  hardener 
must  study  the  nature  of  steel.  He  must  know  what 
steel  is  liable  to  do  under  certain  conditions,  and  how 
to  avoid  undesirable  results.  No  matter  whether  it  re- 
lates to  his  department  or  some  other  department,  he 
should  know  that  it  is  possible  for  the  tool  maker  to 
treat  the  steel  in  such  a  manner  that  results  anything 
but  satisfactory  must  follow  when  it  is  hardened.  He 
should  also  imderstand  that  he  may  make  the  steel  un- 

80 


The  wrong  way  to  anneal. 

fit  for  use  by  overheating  when  annealing,  or  he  may 
not  heat  it  uniformly  throughout,  and  consequently 
does  not  remove  the  tendency  to  spring  from  internal 
strains.  If  a  satisfactory  steel  is  furnished,  the  hard- 
ener should  never  blame  the  steel  for  bad  results  which 
are  caused  by  his  ignorance  or  carelessness,  because  he 
may  be  furnished  with  an  undesirable  steel  next  time. 
And  in  time  those  over  him  in  authority  will  tire  of 
complaints  about  a  steel  that  another  concern  is  satisfied 
with. 

A  method  of  annealing  steel  which  the  writer  has 
seen  practiced  in  some  shops,  but  which  should  never 
be  used  when  annealing  tool  steel,  is  to  pack  the  articles 
in  a  box  with  cast  iron  dust  or  chips.  Now  this  method 
works  nicely  when  annealing  forgings  or  other  pieces 
of  machinery  steel  which  were  hard  and  show  glassy 
spots  and  cannot  be  softened  by  the  ordinary  processes 
of  annealing.  The  cast  iron  seems  to  have  an  affinity 
for  the  impurities  liable  to  be  present  in  the  low  grade 
steels,  and  the  result  is  very  soft  and  easily  worked 
pieces.  But  if  the  method  is  applied  to  tool  steel  the 
carbon  is  extracted  to  an  extent  which  is  highly  injur- 
ious to  it.  To  be  sure,  tool  steel  can  be  annealed  very 
soft  if  packed  as  described,  but  the  result  is  anything 
but  desirable. 

The  writer  had  charge  at  one  time  of  a  hardening 
plant  where,  among  other  things,  many  hundred  pairs 
of  bicycle  cranks  were  hardened  every  week.  A  lot 
of  ten  thousand  crank  forgings  were  received  and 
started  through  the  regular  routine  necessary  to  get 
them  in  a  condition  for  hardening.  When  the  first 
batch  reached  the  hardener  it  was  found  impossible  to 
harden  them  by  ordinary  processes.     And,  by  the  way, 

8i 


Results  from  wrong  annealing. 


samples  had  been  forged  and  sent  us  ahead  of  the  main 
batch  which  had  been  tested  and  found  all  right.  They 
hardened  and  tempered  in  a  satisfactory  manner  and 
stood  the  required  tests. 

The  first  test  was  made  by  placing  each  end  of  the 
crank  on  the  two  projections  of  an  iron  block,  as  shown 
in  Fig.  29,  and  struck  in  the  center  a  blow  with  a 
heavy  hammer  in  the  hands  of  an  experienced  inspec- 
tor. They  were  then  taken  to  a  testing  machine  and 
given  a  very  severe  test,  which  consisted  in  holding 
the  end  which  went  on  the  axle  in  a  fixed  position. 
Pressure  was  applied  to  the 
other  end  until  the  crank 
was  bent  a  certain  amount. 
The  pressure 
was  removed 
and  the  crank 
was  supposed 
to  come  back 
straight,  but 
the  cranks  in 
the  large 
batch  would 
not  harden. 

Investigation  at  the  forge  shop  where  we  procured 
them,  showed  that  through  some  mistake  the  cranks, 
after  being  forged,  were  packed  in  cast  iron  dust  or 
chips  in  the  annealing  pot.  Orders  had  been  given  to 
anneal  some  machine  steel  forgings  in  this  manner  and 
to  anneal  the  cranks  in  charcoal,  but  someone  got  the 
orders  mixed,  and  hence  the  trouble.  The  cranks  were 
made  of  40-point  carbon  open  hearth  steel.  We  reme- 
died the  defect  by  packing  them  in  iron  boxes  with 

82 


The  Derry  Collard  Co. 


Figure  29.      Testing  a  bicycle  crank. 


"Expended  bone"  for  annealing. 

wood  charcoal,  and  submitting  them  to  heat  in  the 
furnace  for  several  hours  after  they  were  red-hot.  In 
this  way  we  got  them  in  condition  to  harden. 

Another  method  which  works  nicely  when  applied 
to  annealing  machinery  steel,  but  which  is  entirely  un- 
fitted for  tool  steel,  is  to  pack  the  pieces  in  annealing 
boxes  in  expended  bone — i.  e.,  bone  that  has  been 
previously  used  in  case  hardening.  As  before  stated, 
machinery  steel  packed  in  this  manner,  and  heated, 
gives  excellent  results.  It  is  also  an  excellent  way  of 
annealing  cast  iron  (by  this  is  meant  small  castings,  as 
typewriter  parts,  etc. ,  which  must  be  very  soft  in  order 
to  machine  nicely). 

But  tool  steel  should  never  be  packed  in  any  form 
of  bone,  as  bone  contains  phosphorus,  and  this  is  the 
most  injurious  of  any  of  the  impurities  which  tool  steel 
contains.  The  steel  maker  uses  every  eJffort  possible 
to  reduce  the  percentage  of  this  impurity  to  the  lowest 
possible  point,  for  while  it  is  a  hardening  agent,  its 
presence  makes  tool  steel  brittle,  so  that  it  is  folly  to 
pay  a  good  price  for  steel  on  which  the  manufacturer 
has  spent  much  time  and  money  to  rid  of  undesirable 
impurities  and  consequently  must  charge  a  high  price 
for,  and  then  use  some  method  whereby  the  steel  is 
charged  with  these  very  impurities. 

In  concluding,  it  may  not  be  amiss  to  emphasize  a 
few  facts  that  have  already  been  mentioned.  Do  not 
overheat  steel  when  annealing  or  it  will  be  perma- 
nently injured.  Do  not  subject  it  to  heat  for  a  longer 
period  of  time  after  it  becomes  uniformly  heated 
throughout  than  is  necessary  to  accomplish  the  desired 
result.  For  while  it  is  necessary  to  heat  the  steel  when 
annealing  to  as  high  a  heat  as  will  be  needed  in  harden- 

83 


Uniform  annealing  heat  necessary. 

ing,  and  while  the  steel  must  be  subjected  for  a  period 
of  time  to  heat  that  insures  its  being  of  the  same  tem- 
perature in  the  middle  of  the  piece  as  it  is  at  the  sur- 
face, yet  we  must  be  careful  not  to  overdo  it. 

Steel  kept  at  a  red  heat  for  a  long  period  of  time, 
even  if  it  is  not  overheated,  will  betray  the  fact  when 
the  temper  is  drawn  after  hardening,  if  it  does  not  at 
any  other  time.  A  piece  of  steel  which  is  kept  hot  for 
too  long  a  period  when  annealing,  may  apparently 
harden  all  right,  but  when  the  temper  is  drawn  the 
hardness  apparently  runs  out — i.  e.,  when  the  piece  is 
heated  to  a  straw  color  it  may  be  filed  very  readily, 
whereas  a  piece  from  the  same  bar  not  annealed,  or 
which  was  properly  annealed  and  then  hardened  and 
drawn  to  the  same  temper  color,  would  show  all  right 
— i.  e.,  a  file  would  just  catch  it. 

Uniform  temperature  when  heating  for  annealing 
is  as  desirable  as  when  heating  for  hardening.  If  a 
large  block  is  unevenly  heated,  its  corners  and  edges 
are  hotter  than  the  main  part  of  the  block.  Violent 
strains  are  set  up  at  these  points,  so  it  will  be  readily 
apparent  that  uniform  heating  during  the  various  pro- 
cesses is  one  of  the  secrets  of  successful  hardening  of 
tool  steel. 

There  are  other  methods  of  annealing  steel, 
methods  whereby  the  surface  does  not  become  oxidized 
by  the  process  of  heating,  as  when  heating  drill  rods, 
etc. ,  but  as  these  methods  are  not  likely  to  be  used  by 
mechanics  in  every  day  shops,  their  consideration 
would  be  entirely  out  of  place  at  this  time. 

Lastly,  remember  that  any  process  of  annealing 
that  takes  from  the  steel  any  of  its  hardening  proper- 
ties should  never  be  used,  no  matter  how   soft  it  will 

84 


Baths  for  hardening. 

make  the  steel.  It  is  better  to  work  a  piece  of  steel 
which  is  hard,  than  to  unfit  it  for  doing  its  maximum 
amount  of  duty  when  finished ;  but  it  is  possible  to  an- 
neal most  steel  so  that  it  will  be  workable  and  yet 
harden  in  a  satisfactory  manner ;  in  fact,  in  a  much  more 
satisfactory  manner  than  if  not  annealed. 

When  annealing  high  carbon  steel,  and  it  is  desir- 
able to  retain  the  full  amount  of  carbon  in  the  steel,  it 
is  advisable  to  pack  in  the  annealing  box  with  charred 
leather,  instead  of  wood  charcoal. 

When  it  is  desirable  to  harden  the  surface  of  low 
carbon  steel  harder  than  it  would  naturally  be,  it  may 
be  machined  nearly  to  size,  packed  in  a  box  with  charred 
leather  and  run  for  a  length  of  time  sufficient  to  give 
the  desired  results.  After  machining  to  shape,  it  may 
be  hardened  in  the  ordinary  manner. 

Hardening  Baths. 


When  steel  is  heated  to  the  proper  hardening  heat 
it  is  plunged  into  some  cooling  bath  to  harden.  The 
rapidity  with  which  the  heat  is  absorbed  by  the  bath 
determines  the  hardness  of  the  steel.  Knowing  this, 
it  is  possible  by  the  use  of  baths  of  various  kinds  to 
give  steel  the  different  degrees  of  hardness  and  tough- 
ness. A  bath  that  will  absorb  the  heat  contained  in  a 
piece  of  steel  the  quickest,  will  make  it  the  hardest, 
everything  else  being  equal.  A  bath  of  mercury  will 
cause  a  piece  of  steel  plunged  in  it  to  be  harder  than  if 
it  were  plunged  in  any  of  the  liquids  commonly  used 

85 


Brine  in  "saturated  solution." 

for  this  purpose,  but  as  such  a  bath  would  be  extremely- 
expensive,  it  is  but  little  used.  Clear  cold  water  is  the 
one  more  commonly  used  than  any  other,  and  for  most 
cutting  and  similar  tools  gives  good  satisfaction, 
although  many  old  hardeners  claim  better  success  with 
water  that  has  been  boiled,  or  that  has  been  used  for 
some  time,  provided  it  is  not  dirty  or  greasy. 

A  very  excellent  bath  that  is  used  very  extensively 
is  made  by  dissolving  all  the  salt  possible  in  a  tank  of 
water,  or  what  is  known  as  a  ''saturated  solution." 
Salt  water,  or  "brine,"  as  it  is  commonly  called,  is 
used  in  most  shops  on  certain  classes  of  work,  and  in 
some  shops  it  is  used  altogether  where  a  bath  of  water 
is  desired. 

Different  kinds  of  oil  are  also  used  to  accomplish 
various  results.  When  small  or  thin  cutting  tools  re- 
quiring a  hard  cutting  edge  are  to  be  hardened,  a  bath 
of  raw  linseed  oil,  or  neat's  foot  oil,  is  used. 

When  toughness  is  the  desired  quality,  as  in  harden- 
ing a  spring,  a  bath  of  tallow,  sperm  oil  or  lard  oil  is 
used.  But  the  nature  of  steel  of  different  makes  varies 
so  much  that  no  one  bath  answers  best  for  all  purposes, 
or  for  the  same  purpose,  when  applied  to  steels  of  dif- 
ferent makes.  Sometimes  it  becomes  necessary  to  use 
a  bath  containing  two  or  three  ingredients  in  order  to 
accomplish  the  desired  result. 

I  have  in  mind  a  manufacturing  concern  who  made 
a  great  many  heavy  springs.  Until  they  changed  the 
make  of  steel  they  had  been  using  for  years  they  had 
excellent  results  from  hardening  in  lard  oil,  but  after 
changing  they  could  do  nothing  with  this  bath.  After 
considerable  experimenting  they  were  advised  to  use 
the  following  mixture :      Spermaceti  oil  48  parts,  neat's 

?6 


Bath  for  hardening  and  toughening. 

foot  oil  45  parts,  rendered  beef  suet  4  parts,  resin  3 
parts.  They  had  very  good  results  with  this  bath  until 
a  drummer  came  along  with  good  cigars  and  a  steel 
two  cents  a  pound  cheaper,  and  then  trouble  was  the 
result. 

By  the  way,  I  have  visited  and  known  of  several 
shops  where  a  few  good  cigars  or  an  occasional  wine 
supper,  which  some  glib-tongued  salesman  was  willing 
to  put  up  for  the  man  who  did  the  buying,  caused  more 
trouble  than  a  little  in  the  hardening  department.  But 
to  return  to  the  hardening  of  the  springs.  When  the 
new  steel  came,  the  springs  would  not  harden  sufficiently 
in  the  mixture  mentioned.  They  were  finally  advised 
to  try  a  bath  of  boiling  water,  and  this  worked  very 
nicely. 

Very  small  cutting  tools,  as  taps,  reamers,  counter- 
bores,  etc. ,  harden  nicely  in  a  bath  made  by  dissolving 
one  pound  of  citric  acid  crystals  in  one  gallon  of  water. 
This  proportion  may  be  used  in  making  a  bath  of  any 
size. 

The  following  is  recommended  when  it  is  desired 
to  have  the  tools  hard  and  tough : 

Salt Yt,  teacupf ul. 

Saltpetre ^  ounce. 

Pulverized  alum i  teaspoonf ul. 

Soft  water i   gallon. 

The  following  bath  gives  excellent  results,  but  care 
must  be  exercised  in  its  use,  as  it  is  deadly  poison.  To 
six  quarts  of  soft  water  put  in  one  ounce  of  corrosive 
sublimate  and  two  handfuls  of  common  table  salt. 
When  dissolved  it  is  ready  for  use. 

Sulphuric  acid  is  added  to  water  in  various  pro- 
portions,  from  one  part  acid  to  ten  parts  water,   to 

87 


■Rotting"  steel  by  add  baths. 


lllllllllill  II 

IL!|i!lll|i'!!!ll!ii:il 


i!io)i]j{[[;i-i 


TTmrrrTTTTTTTTT 
i     :i!|l|  I 


equal  parts  of  acid  and  water.  Some  even  use  clear 
acid,  and  although  excellent  results,  so  far  as  the 
hardened  surface  is  concerned,  may  be  obtained  by  the 
use  of  this  acid,  steel  makers  do  not  advocate  its  use, 
claiming  that  the  after-effects  are  injurious  to  the 
steel,  that  is,  it  '•"rots'"  the  steel,  and  the  writer's  ex- 
perience substantiates  the  claims  of  the  steel  makers. 
I  do  not  advocate  the  use  of  any  of  the  acids  which  act 
directly  on  steel,  provided  any  other  form  of  bath  will 
give  satisfactory  results. 

There  are  many  other  compounds  used  with  suc- 
cess in  various  shops.     Some  of  these  will  be  mentioned 

in  connection  with 
hardening  various 
tools.  As  a  rule, 
tool  steel  that  is  fit 
for  use  for  cutting 
tools  will  harden  in  a 
satisfactory  manner 
in  clear  water.  If  the 
outline  is  irregular  or 
it  is  desirable  that 
it  should  be  extra 
hard,  a  bath  of  brine 
answers  admirably. 
Articles  of  an  irregu- 
lar shape  made  of 
steel  liable  to  crack 
when  hardened  should  be  dipped  in  water  or  brine  (that 
is,  warmed  somewhat),  the  temperature  of  the  bath  de- 
pending upon  the  liability  of  the  piece  to  crack. 

Tools,  as  milling  cutters,  made  from  high  carbon 
steel,  are  many  times  hardened  to  advantage  in  a  bath 


^/.W////////////M'/;7777Z^^. 


The  Detry  CoUard  Co, 

Figure  30.     Oil  and  water  bath 
for  hardening. 


Methods  of  cooling  for  hardening. 


of  water  having  one  or  two  inches  of  oil  on  the  surface, 
as  shown  in  Fig.  30.  The  article  is  brought  to  the 
proper  temperature  in  the  fire  and  immersed  in  the 
bath,  passing  it  down  through  the  oil  into  the  water. 
Enough  oil  adheres  to  the  red  hot  steel,  especially  in 
the  corners  of 
the  teeth  or 
projections,  to 
prevent  the 
water  acting  as 
suddenly  as  it 
otherwise 
would,  thus  do- 
ing away  in  a 
great  measure 
with  the  ten- 
dency to  crack. 
It  is  a  good 
plan  when  hard- 
ening  large 
pieces  of  almost 
any  shape  to 
first  dip  in  water 

or  brine  and  allow  them  to  remain  in  this  liquid  until 
the  surface  is  hard,  then  remove  and  instantly  plunge 
into  a  tank  of  oil,  allowing  them  to  remain  in  the  oil 
until  cold.  This  works  especially  well  in  the  case  of 
such  tools  as  milling  machine  cutters,  punching  press 
dies,  etc. ,  where  it  is  not  necessary  that  the  hardened 
surface  be  very  deep. 

The  depth  to  which  a  piece  is  hardened  depends 
on  the  length  of  time  it  is  left  in  the  water.  For  this 
purpose  old  hardeners  allow  the  article  to  remain  in  the 

89 


Supply 

Ov«cfloyy 

Figure  3 1 .     Hardening  with  jet 
from  bottom. 


Various  cooling  methods. 

water  until  it  ceases  to  "sing."  This  is  the  peculiar 
noise  occasioned  by  putting  a  piece  of  red  hot  steel  in 
water.  When  the  piece  stops  singing  it  is  removed 
from  the  water  and  plunged  in  oil  and  left  until  cold. 

When  pieces  are  to 
be  hardened,  and  it  is 
necessary  to  harden 
the  walls  of  a  hole  or 
some  depression,  as 
the  face  of  an  impres- 
sion die,  or  forming 
die,  or  any  similar 
piece,  it  is  necessary  if 
good  results  are  de- 
sired, to  have  a  bath 
which  has  a  stream  or 
jet  coming  up  from  the 
bottom,  as  shown  in 
Fig.  31.   If  clear  water 


The  Derrjs  Collard  CO. 


Figure  32.     Continuous  brine  bath. 


is  used  in  the  bath,  the  inlet  pipe  may  be  connected 
with  some  constant  supply,  but  if  brine  or  some  solu- 
tion is  used,  it  becomes  necessary  to  have  a  supply  tank 
having  a  pump  as  shown  in  Fig.  32.     The  contents  of 


90 


Various  cooling  methods. 


the  bath  are  pumped  into  the  supply  tank  and  run 

down  the  supply  pipe  as  shown. 

At  times  it  is  desirable  to  have  a  tank  in  which 

there  is  no  gush 
or  jet  of  fluid,  but 
where  the  con- 
tents of  the  bath 
are  kept  in  mo- 
tion in  order  to 
force  the  steam 
away  from  the 
surface  to  be 
hardened.  There 
are  several  ways 
of  accomplishing 
this.  Fig.  33 
shows  a  bath  hav- 
ing a  pipe  com- 
ing up  from  the 


'}//////////////////y///?/////, 


■mM^s^^^ 


The  Derry  CoUard,  Co. 


Figure  33.     Bath  with  perforated 
bottom  plate. 


bottom,  the  jet  striking  the  plate  which 
spreads  the  fluid.  It  then  comes  to  the  sur- 
face through  the  perforated  plate  shown. 

Fig.  34  shows  a  bath  in  which  the 
contents  are 
kept  in  motion 
by  some  me- 
chanical means 
contained  in  the 
tank.  Such  a 
bath  may  be 
made  by  follow- 
ing the  sugges- 
tions   contained  Figure  34.     Bath  with  agitator. 

9» 


V<-f-^'^^^'';^c^^^fh^^^=i^i^^'-^i^^''i^, 


Ml 


About  heating  baths. 

in  the  illustration.  A  tank  of  any  convenient  size 
may  be  made  having  a  partition  as  shown.  The  por- 
tion of  the  tank  marked  a  is  intended  to  be  used 
for  the  immersion  of  the  articles  being  hardened, 
while  b  contains  a  pump,  Archimedian  screw  or  some 
similar  device  for  forcing  the  water  into  the  side  a. 

If  a  pump  is  used,  the  water  is  forced  through  the 
pipe  shown.  If  an  Archimedian  screw  is  used,  the  parti- 
tion shown  should  not  extend  way  to  the  bottom,  the 
water  being  forced  under  it.  In  either  case  it  returns 
to  h  over  the  top  of  the  partition  c  as  shown,  thus 
insuring  a  rapid  circulation  of  fluid.  This  form  of  bath 
is  especially  to  be  desired  where  brine  or  some  favorite 
hardening  solution  is  used.  It  is  also  possible  to  heat 
the  contents  of  the  bath  when  it  is  considered  advis- 
able, as  in  the  case  where  articles  are  to  be  hardened 
that  are  liable  to  crack  in  contact  with  extremely  cold 
liquids.  Much  more  uniform  results  may  be  obtained, 
especially  when  small,  thin  pieces  are  hardened,  if  a 
uniform  temperature  can  be  maintained  in  the  bath. 

In  order  to  keep  the  contents  of  the  bath  at  some- 
where near  a  uniform  temperature,  a  small  coil  of 
steam  pipe  may  be  placed  in  the  tank,  and  a  ther- 
mometer may  be  so  placed  as  to  readily  show  the  con- 
dition of  the  bath.  While  it  may  seem  unnecessary  to 
be  so  particular  about  the  temperature  (and  it  is  un- 
necessary on  most  work,  as  an  experienced  hardener 
can  determine  the  temperature  very  closely  by  the 
sense  of  feeling),  yet  there  are  jobs  where  it  is  essential 
that  a  certain  uniform  temperature  be  maintained  in 
order  to  get  uniform  results.  I  do  not  mean  by  this 
that  it  is  practical  to  attempt  to  keep  the  temperature 
within  a  few  degrees  of  a  given  point,  but  it  can  be 

9* 


Figure  35.     Die  with  hole. 


Cooling  dies  with  holes. 

kept  somewhere  near  in  order  to  get  the  best  results 

possible. 

Sometimes  it  is  necessary  to  harden  the  walls  of  a 

hole  that  does  not  go  way  through  the  piece,  as  a  die 

used  for  compression  work  or 

some  forms  of  dies  for  striking 

up  cylindrical  pieces.     Fig.  35 

shows  a  sectional  view  of  a  die 

having  a  hole  part  way  through 

it  as  described.     Now,  if  a  piece 

of  work  of  this  description  were 

hardened  in  a  bath  where  the 

contents  were  not  agitated,  it 

is  doubtful  if  the  walls  of  the  hole  would  be  hardened 

in  the  least.     The  steam  generated  would  blow  the 
liquid   out  of  the  hole,    and    none 
could  enter  until  the  steel  was  cooled 
to  a  point  where  it  could  not  harden. 
Better  success  would 
follow  if  it  were  dipped 
in  a  bath  having  a  jet 
of  water  coming  up  from 
the  bottom  of  the  tank, 
but  in  this  case  it  would 
be  necessary  to   invert 
the  piece  in  order  to  get 
the  liquid  to  enter  the 
hole,    and    if    it    were 

dipped   in  this  position,   it  is  probable  that   enough 

steam  would  rise  to  keep  the  contents  of  the  bath  from 

affecting  the  walls  near  the  bottom. 

Now,  in  order  to  get  satisfactory  results  when 

hardening  work  of  this  character,  it  will  be  found  best 


Figure  36.     Method  of  cooling 
holes  in  dies. 


93 


Cooling  a  shank  mill. 

to  have  a  bath  so  constructed  that  the   liquid  can  run 
into  the  hole  by  means  of  a  faucet  or  pipe,  as  shown  in 

Fig.    36.     If  the  hole   is  deep  and  

there  is  danger  of  the  steam  pre- 
venting the  liquid  effectually  work- 
ing at  the  bottom,  a  pipe  may  be  run 
nearly  to  the  bottom,  as  shown  in  the 
sectional  view  of  Fig.  37.  The  pipe 
must  not  be  as  large  as  the  hole,  or 
the  results  will  not  be  satisfactory. 


Figure  37.     Cooling  a  deep 
hole  in  a  die. 

Sometimes  it  is  necessary  to 
harden  several  pieces  of  a  kind 
whose  outline  betokens  trouble 
if  dipped  in  a  cold  bath,  and 
yet  it  seems  necessary  to  use  a 
cold  bath  in  order  to  get  the 
desired  result.  Take,  for  in- 
stance, a  shank  mill  of  the 
shape  shown  in  Fig.  38.  If  this 
mill  is  heated  to  the  proper  degree  of  heat  and  plunged 
in  a  dish  containing  just  enough  water  or  other  liquid 
to  harden  the  teeth  before  the  water  gets  hot,  the  teeth 


Tlw  Derry  Collurd  Co, 


Figure  38.     Cooling  a 
shank  mill. 


94 


About  using  dirty  water. 

will  harden  in  a  satisfactory  manner,  and  the  water  will 
heat  so  as  to  do  away  with  any  danger  of  cracking  the 
cutter  from  internal  strains.  The  size  of  the  dish  will 
determine  the  depth  of  the  hardening.  When  one 
piece  is  hardened  the  dish  may  be  emptied  and  filled 
with  cold  water  for  the  next. 

The  writer  has  seen  this  scheme  used  with  excel- 
lent results,  not  only  on  milling  cutters,  but  on 
broaches,  small  dies,  etc.,  that  showed  a  tendency  to 
crack  when  dipped  in  a  large  bath  of  cold  fluid.  Of 
course,  it  should  be  borne  in  mind  that  the  dish 
selected  for  the  bath  must  be  large  enough  to  hold  a 
sufficient  amount  of  liquid  to  harden  the  piece  the 
necessary  amount  before  it  becomes  too  hot,  but  it  is 
also  essential  that  it  should  not  be  so  large  that  the 
contents  Vs^ill  not  heat,  because  then  there  is  no  differ- 
ence in  its  action  from  that  of  a  large  bath. 

Generally  speaking,  however,  it  is  advisable  to  use 
a  large  bath,  having  the  contents  at  a  temperature  of 
about  60  degrees  Fahr.,  as  then  the  process  of  con- 
traction, which  takes  place  when  the  piece  is  cooling, 
is  uniform. 

Delicate  articles,  however,  require  a  bath  having 
the  contents  heated  somewhat  above  the  temperature 
mentioned,  the  temperature  depending  on  the  character 
of  the  article  and  the  nature  of  the  steel. 

It  should  be  borne  in  mind  that  a  tank  or  dish  of 
dirty  water  makes  a  very  undesirable  bath;  neither 
should  one  be  used  having  dirt  in  the  bottom,  because 
as  the  contents  are  agitated,  the  dirt  rises,  preventing 
the  liquid  acting  in  a  satisfactory  manner. 


n 


Baths  for  Hardening. 

The  Lead  Bath. 

When  comparatively  small  pieces  of  work  are  to 
be  hardened  in  large  quantities,  as,  for  instance,  the 
various  small  parts  of  bicycles,  sewing  machines  and 
guns,  red-hot  lead  furnishes  an  excellent  means  of 
uniformly  heating  in  a  very  economical  manner.  It 
is  a  speedy,  and  at  the  same  time  a  very  reliable 
means  to  use,  as  the  heat  can  be  maintained  so  uni- 
formly, it  can  be  applied  safely.  By  using  a  proper 
amount  of  precaution,  there  is  no  danger  of  burning 
the  outside  of  the  article  before  the  center  is  heated. 
Large  and  small  parts  are  heated  alike,  and  quite  a 
number  of  pieces  can  be  heated  at  the  same  time,  thus 
making  it  a  cheap,  rapid,  yet  reliable  way  of  heating. 
It  is  necessary  to  have  a  uniform  heat  under  and 
around  the  crucible  that  can  be  maintained  for  quite  a 
length  of  time. 

A  furnace  burning  illuminating  gas  as  fuel,  gives 
the  most  satisfactory  results,  although  excellent  results 
may  be  obtained  by  the  use  of  a  furnace  burning  gaso- 
line or  crude  oil.  If  it  is  not  found  possible  to  obtain 
any  of  these,  good  results  can  be  obtained  by  the  use 
of  one  burning  charcoal,  hard  coal,  or  coke;  but  in 
order  to  obtain  uniform  results,  a  great  deal  of  atten- 
tion must  be  paid  to  the  fire. 

If  but  a  few  pieces  are  to  be  hardened  at  a  time, 

96 


About  lead  and  crucibles. 

and  it  is  not  considered  advisable  to  purchase  or  make 
a  furnace  especially  adapted  to  this  kind  of  work,  a 
crucible  may  be  placed  in  a  fire  on  an  ordinary  black- 
smith's forge.  Build  up  around  it  with  bricks,  placed 
far  enough  away  from  the  crucible  to  have  a  fire  all 
around  it,  and  fill  this  space  with  charcoal.  It  will  be 
found  necessary  to  raise  the  crucible  occasionally  and 
poke  coals  under  it. 

The  most  satisfactory  crucible  is  one  made  of 
graphite,  especially  for  this  purpose.  A  cast  iron  one 
is  sometimes  used,  but  as  a  rule  is  not  as  satisfactory 
and  is  more  costly,  as  it  burns  out  very  quickly. 

The  graphite  crucible  should  be  annealed  before 
using,  as  this  toughens  it,  reduces  the  liability  of 
cracking  and  makes  it  longer  lived.  In  order  to  anneal 
the  black  lead  crucible,  place  it  in  any  oven  or  furnace 
where  a  uniform  heat  can  be  obtained,  heat  it  to  a  red, 
take  it  out  and  place  it  where  it  can  cool  off  slowly 
without  any  drafts  of  air  striking  it. 

It  is  very  essential  that  the  proper  quality  of  lead 
is  used.  Red-hot  steel  is  very  susceptible  to  the  action 
of  certain  impurities.  Many  brands  of  lead  contain 
sulphur  in  such  quantities  that  it  is  very  injurious  to 
the  steel.  Nothing  but  chemically  pure  leads  should 
be  used.  It  is  the  custom  in  some  shops  to  use  lead  of 
any  kind,  and  when  unsatisfactory  results  are  obtained, 
the  method,  instead  of  the  material,  is  condemned,  be- 
cause the  operator  does  not  understand  the  cause  of 
the  trouble. 

If  the  lead  contains  sulphur,  even  in  small  quanti- 
ties, it  will  ruin  the  steel.  The  article  will  have  a 
honeycomb  appearance,  and  portions  of  the  outside 
stock  will  be  eaten  away.     When  using  lead  that  is 

97 


Mixture  for  hardening  small  tools. 

chemically  pure,  this  difficulty  will  not  be  encountered. 
Many  hardeners  are  averse  to  the  use  of  the  lead 
bath  in  hardening  on  account  of  the  tendency  of  the 
lead  to  stick  to  the  work.  To  prevent  this  trouble, 
different  compounds  are  used. 

The  writer  has  had  excellent  results  with  a  solu- 
tion of  cyanide  of  potash  in  water.  Dissolve  one 
pound  of  powdered  cyanide  and  one  gallon  of  boiling 
water.  Let  it  cool  before  using.  If  this  should  not 
prove  to  prevent  the  lead  sticking,  put  in  a  larger 
portion  of  cyanide.  Some  use  a  strong  solution  of  salt 
and  water.  Dip  the  articles  in  the  solution;  place 
them  where  they  can  dry,  preferably  in  a  hot  place 
where  they  will  dry  more  rapidly.  It  is  not  safe  to 
put  them  in  the  lead  when  damp,  as  any  moisture 
would  cause  the  lead  to  fly. 

The  writer  has  used  the  following  mixtures  with 
very  gratifying  results  when  hardening  such  work  as 
small  milling  cutters,  taps,  reamers,  broaches,  cherries, 
rotary  files  and  similar  tools  having  fine  teeth  likely  to 
hold  the  lead.  This  formula  is  taken  from  the  report 
of  the  Chief  of  Ordinance  of  the  War  Department,  and 
is  used  in  the  U.  S.  Government  shops  when  harden- 
ing files.  The  following  is  a  copy  of  the  report: 
* 'Before  hardening,  the  files  are  treated  with  a  mixture 
of  salt  and  carbonaceous  material  to  protect  the  teeth 
from  decarbonization  and  oxidation.  The  kinds  and 
proportions  of  the  ingredients  are  exhibited  in  the  fol- 
lowing table : 

Pulverized  charred  leather i  ft). 

Fine  family  flour 1%  ft)S. 

Fine  table  salt 2  ibs. 

The  charcoal  made  from  the  charred  leather  should 

98 


The  hardening  of  files. 

be  titurated  until  fine  enough  to  pass  through  a  No.  45 
sieve.  The  three  ingredients  are  thoroughly  mixed  and 
incorporated  while  in  a  dry  state,  and  the  water  is  then 
added  slowly  to  prevent  lumps,  until  the  paste  formed 
has  the  consistency  of  ordinary  varnish.  When  ready, 
the  paste  is  applied  to  the  file  with  a  brush,  care  being 
taken  to  have  the  teeth  well  filled  with  the  mixture. 
The  surplus  paste  is  then  taken  off  the  file  by  the 
brush,  and  the  file  is  pl&ced  on  end  before  a  slow  fire 
to  dry.  If  dried  too  quickly  the  paste  will  crack  or 
blister.  If  not  dry  enough,  the  remaining  moisture 
will  be  transformed  into  steam  when  dipped  into  the 
hot  lead  bath,  and  cause  an  ebullition  or  sputtering  of 
the  lead,  throwing  out  minute  globules  of  the  latter, 
which  may  endanger  the  eyes  of  the  operator.  The 
fusing  of  the  paste  upon  the  surface  of  the  file,  indi- 
cates the  proper  heat  at  which  the  file  should  be 
hardened." 

File  makers  have  methods  of  hardening  files  that 
differ  very  materially  from  the  above  process,  but  it 
has  proved  particularly  valuable  when  applied  to  the 
tools  mentioned.  Small  articles,  if  of  an  even  size  or 
thickness  throughout,  may  be  put  into  the  lead  when 
they  are  cold  and  left  until  red-hot,  although  they 
should  be  turned  over  occasionally.  But  pieces,  such 
as  shank  mills  and  similar  articles  of  irregular  contour, 
having  large  and  small  parts  in  connection  with  each 
other,  should  be  heated  nearly  to  a  red  before  putting 
into  the  lead,  as  the  sudden  expansion  of  the  large 
thin  parts  would  tear  them  from  the  more  solid  por- 
tions that  could  not  heat  and  expand  so  quickly. 

The  purpose  of  putting  such  pieces  into  the  lead  is 
for  the  uniform  heat  that  can  be  finally  obtained  on  the 

99 


Reasons  for  heating  in  lead. 

unequal  sizes  and  thicknesses,  making  them  much  less 
liable  to  crack  when  dipped  in  the  bath.  If  an  irregu- 
lar shaped  piece  were  plunged  suddenly  into  the  red- 
hot  lead,  and  thereby  cracked,  it  probably  would  not  be 
noticed  until  it  was  hardened,  and  the  natural  inference 
would  be  that  it  had  cracked  in  the  cooling  bath ;  but  a 
careful  examination  of  the  fracture  would  show  the 
walls  to  be  black,  proving  it  to  have  been  subject  to 
heat  after  it  was  cracked.  If  it  were  sound  until  dipped 
in  the  bath,  the  walls  w^ould  have  a  brighter  appear- 
ance, although  it  might  be  somewhat  stained  by  the 
contents  of  the  bath,  yet  they  would  not  be  black. 

The  following  question  may  suggest  itself.  If  the 
piece  of  work  is  to  be  partly  heated  in  another  fire,  why 
not  heat  to  the  hardening  heat?  The  reason  for  this  is, 
that  a  much  more  uniform  heat  can  be  obtained  in  the 
lead  crucible  than  in  an  ordinary  open  fire.  When  it  is 
necessary  to  harden  a  portion  of  the  piece,  leaving  the 
balance  soft,  it  need  only  be  dipped  in  the  lead  the  re- 
quired distance,  moving  it  up  and  down  to  prevent  a 
fire-crack.  It  is  likely  to  crack  at  the  point  where  the 
heat  leaves  off,  just  as  a  piece  of  red-hot  steel  will 
crack  if  dipped  into  water  in  such  a  way  that  some  of 
the  red  is  out  of  the  bath  and  the  piece  held  in  that 
position.  It  then  cracks  at  the  point  where  the  con- 
traction ceases,  while  in  the  first  case  it  cracks  where 
the  expansion  ceases. 

If  impossible  to  do  the  first  heating  in  an  open  fire, 
or  if  it  is  considered  advisable  to  heat  it  in  red-hot  lead 
altogether,  the  piece  may  be  immersed  in  the  lead,  left 
there  for  a  moment  and  withdrawn.  It  may  then  be 
immersed  again,  leaving  a  little  longer  than  the  first 
time  and  withdraw  it  again,  repeating  the  operation 

100 


How  to  handle  lead  for  heating. 

until  the  steel  is  heated  to  a  point  where  the  intense 
heat  will  not  cause  it  to  crack  from  the  sudden  change 
of  temperature. 

To  prevent  dross  from  forming  on  the  lead,  keep 
the  surface  covered  with  broken  charcoal.  This  not 
only  has  a  tendency  to  prevent  dross  forming,  but  the 
charcoal,  catching  fire  and  burning,  keeps  the  surface 


v * 


Figure  39.     Mould  for  casting  lead. 


of  the  lead  at  a  more  uniform  heat,  than  if  not  used. 
But  despite  all  these  precautions,  more  or  less  dross 
will  form  in  the  surface  of  the  lead.  This  should  be 
skimmed  off  occasionally,  in  order  that  it  may  not  stick 
to  the  work. 

When  no  longer  using  the  crucible,  the  lead  should 
be  emptied  out,  as  if  left  in  the  crucible  until  it  cools 
and  solidifies,  the  crucible  will  probably  crack  when  the 
lead  is  heated  again.  It  may  be  removed  by  means  of 
a  ladle  and  emptied  into  small  moulds.    When  the  cru- 


Caution  about  too  hot  lead. 

cible  is  nearly  empty,  it  may  be  lifted  from  the  fire  and 
the  balance  of  the  lead  poured  out.  As  it  is  necessary 
to  put  the  lead  into  the  crucible  in  small  pieces,  it  is 
best  to  use  a  mold  of  the  form  shown  in  Fig.  39,  as  this 
makes  a  very  convenient  size  to  put  into  the  crucible 
again.  To  get  good  results  when  hardening,  the  lead 
should  be  stirred  up  from  the  bottom  occasionally  in 
order  to  equalize  the  heat,  as  it  will  be  hotter  at  the 
bottom  than  it  will  be  toward  the  top. 

When  heating  pieces  with  fine  projections  or  teeth, 
it  is  well  to  use  a  stiff  bristle  brush  to  remove  any  lead 
that  may  stick  in  the  bottom  between  such  projections. 
This  should  be  done  before  dipping  into  the  bath,  to 
prevent  soft  spots.  Steel  will  not  harden  where  lead 
adheres  to  it,  as  the  liquid  in  the  bath  cannot  then 
come  in  contact  with  the  steel. 

There  is  no  one  method  of  heating  steel  which  is 
so  generally  used  that  is  a  source  of  more  annoyance 
than  the  one  under  consideration,  because  attention  is 
not  paid  to  a  few  simple  points.  But  if  a  chemically 
pure  lead  is  used  in  the  crucible,  the  contents  of  the 
crucible  is  stirred  occasionally,  and  as  low  a  heat  as 
possible  is  maintained,  excellent  results  will  follow. 

A  serious  mistake,  which  is  made  many  times,  is 
to  heat  the  lead  too  hot,  leaving  the  piece  of  work  in 
just  long  enough  to  bring  the  surface  to  the  desired 
heat,  then  removing  and  quenching.  The  objection  to 
this  method  is,  the  heat  is  not  uniform  throughout  the 
piece,  consequently  poor  results  follow.  If  the  article 
is  left  in  the  lead  long  enough  to  become  uniformly 
heated  throughout,  it  will  become  too  hot.  If  the  lead 
becomes  too  hot,  it  is  best  to  plunge  a  large  piece  of 
iron  or  scrap  steel  into  it,  allowing  it  to  absorb  the 


Cyanide  solution  before  heating. 


extra  heat,  thus  reducing  it  to  the  proper  temperature. 
It  is  then  safe  to  go  ahead  with  the  heating,  and  not 
until  then.     Do  not  neglect  this  precaution. 

It  will  readily  be  seen  that  the  lead  should  be  of 

about   the  same  temperature  as  the  steel   should  be 

heated,    and   the   articles   left   in   it 

long   enough   to   become   uniformly 

heated  throughout. 


The  hardener  should 
bear  in   mind  that  the 
amount   of    heat    given 
steel  affects  the   struc- 
ture   rather    than    the 
method  of  applying  the 
heat.     In  order  to  use 
this  method  to   advan- 
tage  when  hardening 
large  quantities  of  small 
articles,  quite 
a  number  of 
pieces  may  be 
heated    at    a 
time    in    the 
lead.      This 
may  readily 
be    accom- 
plished by 

Fisurc  40.      Dr/ins  steel  before  heating.  dipping    a 

number  of  pieces  in  the  cyanide  solution,  laying  them 
on  the  top  of  the  furnace  as  shown  in  Fig.  40.  When 
these  are  thoroughly  dried,  place  them  in  the  lead,  dip 
another  batch  in  the  solution,  and  lay  on  the  furnace 
as  described.      By  this  time  the  pieces  in  the  lead  will 


103 


How  to  handle  work  in  lead  furnace. 

be  hot  enough  to  dip  in  the  bath.  As  one  is  taken  from 
the  lead,  another  may  be  taken  from  the  top  of  the 
furnace  and  put  in  its  place,  another  should  be  dipped 
in  the  solution  and  placed  on  the  furnace.  In  this 
way  a  rotation  may  be  kept  up,  which  insures  the 
maximum  amount  of  work  in  a  given  time. 

Before  taking  a  piece  of  work  from  the  lead,  it 
should  be  plunged  below  the  surface  and  held  there 
long  enough  to  equalize  the  heat.  Articles  being 
heated  in  lead  should  be  turned  over  occasionally,  in 
order  that  they  may  heat  uniformly.  If  long  articles 
are  to  be  heated  by  this  means,  it  is  necessary  to  stir 
the  lead  from  the  bottom  frequently,  or  the  piece  will 
be  the  hottest  at  the  end  nearest  the  bottom  of  the 
crucible. 

When  heating  certain  tools,  as  long  reamers, 
broaches,  etc.,  it  is  sometimes  advisable  to  place  a 
piece  of  cyanide  of  potassium  on  the  surface  of  the 
lead.  It  will  fuse  and  remain  for  some  time  in  a  body 
around  the  steel.  The  tool  may  be  raised  and  lowered 
in  the  lead  through  this  melted  cyanide  occasionally, 
and  especially  just  before  quenching  in  the  bath. 

If  the  article  is  dipped  in  a  bath  of  water,  heated 
as  hot  as  it  is  possible  to  hold  the  hand  in,  the  teeth 
will  be  found  very  hard  and  the  tendency  to  spring  or 
crack  will  be  reduced  very  materially.  If  it  is  desirable 
to  have  the  tool  extremely  strong,  that  is,  able  to  stand 
strains,  as  would  be  the  case  if  a  broach  used  for  draw- 
broaching  were  being  hardened,  the  tool  could  be 
heated  as  described  and  quenched  in  a  bath  of  raw 
linseed  oil,  or  into  a  bath  of  sperm  oil  and  tallow,  to 
which  is  added  a  small  quantity  of  resin.  The  amount 
of  resin  added  should  be  very  small,  as  it  has  a  ten- 

104 


Cyanide  of  potassium  bath. 

dency  to  crystallize  the  steel  if  too  great  a  proportion 
is  used.  Generally  speaking,  one  part  resin  to  loo 
parts  of  oil,  or  oil  and  tallow,  will  be  sufficient,  and 
generally  it  will  not  be  found  necessary  to  use  it,  if 
tallow  is  added  to  the  oil. 

Although  red-hot  lead  furnishes  an  excellent  means 
of  heating  small  articles,  and  a  very  satisfactory  method 
of  heating  certain  kinds  of  tools,  yet  for  most  cutting  tools, 
the  writer  has  found  cyanide  of  potassium,  melted  and 
heated  red-hot  in  a  crucible,  or  a  mixture  of  salt  and 
cyanide  of  potassium,  to  give  more  satisfactory  results. 

Cyanide  of  Potassium   Bath. 

Cyanide  of  potassium,  if  placed  in  a  cast  iron  cruci- 
ble and  heated  red-hot,  furnishes  a  method  of  heating 
steel  that  gives  very  excellent  results  in  many  shops. 
This  method  is  employed  very  extensively  in  heat- 
ing   articles   whose 
shape  betokens  soft 
spots  when  hard- 
ened by  the  ordinary 
methods.     It  is  also 
used   in   hardening 
dies  for  transferring 
impressions    onto 
plates  used  in  print- 
ing bank  notes  and 
similar  work. 

The  articles  heat- 


Figurc  41.     Method  of  suspending  work  in 
cyanide  of  potassium. 


ed  by  this  method  are  not  subject  to  oxidation  from 
the  action  of  the  air  on  the  surface.  The  cyanide  does 
not  have  a  tendency  to  stick  to  the  work,  and  the  action 


[05 


The  action  of  cyanide. 


of  the  cyanide  tends  to  increase  the  surface  hardness, 
thereby  making   the   tools   more   durable   than   when 
hardened  by  ordinary  methods. 
Many  dies  with  finely  engraved 
working  surfaces  are  heated  by 
this  method  and 
the  best  of  re- 
sults   obtained. 
In  order  to  get 
satisfactory   re- 
sults, it  is  neces- 
sary to  use  chem- 
ically pure  cya- 
nide of  potas- 
sium. 

It  is  different 
from  red-hot 
lead  in  that  iron 
will  not  float  on 
its  surface,  but 
sinks  to  the  bot- 
tom,  conse- 
quently it  is 
necessary  to 
suspend  the 
pieces  being 
heated  with 
wires  which 
pass  over  the 
edge  of  the  cru- 
cible in  the  form 
of  a  hook,  as 
showninFig.  41. 


Figure  42.      Cyanide  hardening  furnace, 
also  shown  in  Figure  1 8. 


106 


About  attention  to  heat. 

As  cyanide  of  potassium  is  a  violent  poison,  the 
greatest  care  should  be  exercised  wlien  using  it.  The 
fumes  of  this  chemical  are  very  injurious  to  the  work- 
man, consequently  a  furnace  should  be  used  having 
some  means  of  conveying  the  fumes  into  a  chimney  or 
ventilating  shaft. 

A  furnace  may  be  procured  of  the  pattern  shown 
in  Fig.  42,  using  illuminating  gas  as  fuel.  A  is  the 
pipe  furnishing  fuel  to  the  burners,  B  the  crucible,  C 
the  hood,  D  the  door,  E  the  pipe  which  conducts  the 
products  of  combustion  to  the  pipe  F,  the  pipe  which 
conveys  the  fumes  and  products  of  combustion  into 
the  chimney.  The  lighting  holes  are  stopped  by  the 
fire  clay  plugs  G  G. 

If  it  is  considered  advisable  to  make  a  furnace 
burning  hard  coal  or  coke,  the  same  design  may  be 
used  as  illustrated  in  Fig.  19.  For  a  lead  hardening 
furnace,  a  hood  must  be  added  to  prevent  the  poison- 
ous vapors  getting  into  the  room.  This  hood  must  be 
connected  with  the  chimney. 

The  operator  must  bear  in  mind  that  in  order  to 
get  satisfactory  results,  attention  must  be  paid  to  the 
amount  of  heat  given  the  piece  of  steel,  as  previously 
explained.  The  strength  of  the  hardened  piece  depends 
in  a  greater  measure  than  mechanics  generally  realize, 
on  the  amount  of  heat  given  when  hardening.  In 
order  to  get  the  best  results  possible,  it  is  necessary  to 
have  the  steel  at  the  refining  heat. 

It  is  easy  to  be  deceived  when  heating  by  the 
method  under  consideration,  as  the  effect  of  the  cyanide 
is  to  cause  the  surface  of  steel  to  harden  at  a  tempera- 
ture lower  than  the  ^  refining  heat.  Consequently  the 
portion  beneath  the  surface  may  not  be  hardened  at  all 

107 


How  to  obtain  colors. 


when  the  surface  shows  hard,  if  tested  with  a  file.  It 
matters  not  by  what  method  steel  is  heated  for  harden- 
ing, there  is  a  temperature  at  which  it  should  be 
quenched.  If  not  heated  to  that  temperature,  it  is  not 
as  hard  as  it  should  be  to  accomplish  the  maximum 
amount  of  work  possible.  If  heated  to  a  higher  tem- 
perature, the  pores  are  opened,  the  steel  made  brittle 
and  it  is  unfitted  to  do  the  amount  of  work  it  should. 

Not  only  is  this  method  valuable  because  it  fur- 
nishes a  means  of  heating  steel  uniformly  without 
danger  of  its  sur- 
face becoming 
oxidized,  but  if 
certain  points  are 
observed,  the 
most  beautiful 
colors  imagin- 
able may  be  ob- 
tained. It  is  nec- 
essary, in  order 
to  procure  nice 
colors  on  the 

hardened  product,  that  it  be  nicely  polished,  and  free 
from  dirt  and  grease.  While  grease  will  bum  when 
subjected  to  a  red  heat,  yet  it  leaves  a  stain  on 
the  work. 

When  colors  are  wanted,  articles  made  of  tool  steel 
may  be  suspended  in  the  molten  cyanide  by  means  of 
wire  hooks,  which  pass  over  the  edge  of  crucible,  as 
shown  in  Fig.  43.  When  the  article  becomes  heated 
to  a  uniform  heat,  it  may  be  removed  and  plunged  in  a 
tank  of  water,  working  it  around  well  until  cold,  when 
it  may  be  removed  and  dried.     If  it  is  desirable  to  draw 

108 


Tlie  Derry  CoUard  Co. 

Figure  43.     Heating  in  cyanide  for  colors. 


Hardening  gun  frames  in  colors. 

tlie  temper  and  yet  retain  the  colors,  it  may  be  done 
by  heating  in  a  kettle  of  oil,  guaging  the  heat  by  a 
thermometer.  The  work  must  be  left  in  the  oil,  away 
from  the  action  of  the  air,  until  it  is  cooled  below  the 
point  where  temper  colors  are  visible. 

This  method  of  hardening  is  used  very  extensively 

in  gun  shops  to 
harden  gun 
frames,  and  at 
the  same  time 
procure  the  beau- 
tiful colors  often 
seen  on  them.  It 
works  equally 
well  on  machin- 
ery steel  or  mal- 
1  cable  iron.  It 
is  accomplished 
by  attaching  a 
piece  of  wire  bent 
in  the  shape  of 
a  hook  to  the 
frame,  the  other 
end  of  the  hook 
hangs  over  the 
upper  edge  of  the 
crucible.  It  is 
necessary  to  have 
the  article  entire- 


Mm 


The  Derry  Collard  Co. 

Figure  44.     Method  for  obtaining  vine 
effect  on  tempered  work. 


ly  under  the  surface  of  the  cyanide.  When  it  is 
heated  for  a  sufficient  length  of  time,  which  must  be 
determined  by  experiment,  it  may  be  removed  and 
plunged  in  a  tank  of  water.     In  order  to  produce  the 


109 


Hardening  malleable  iron. 

beautiful  vine-like  effect  often  noticed,  the  inlet  pipe 
may  be  situated  about  two  feet  above  the  tank,  as 
shown  in  Fig.  44.  The  end  of  the  pipe  may  be  made 
to  spray  the  water.  The  articles  when  taken  from 
the  cyanide  crucible  should  be  passed  through  the 
spray  into  the  bath.  Wherever  the  fine  spray  strikes, 
it  produces  the  vine-like  effect  mentioned.  The  colors 
may  be  guaged  by  the  heat  given  the  contents  of  the 
crucible,  also  by  the  temperature  of  the  bath. 

After  using,  a  hook  must  be  thoroughly  dried  be- 
fore putting  in  the  molten  cyanide,  as  the  presence  of 
moisture,  even  in  the  most  minute  quantities,  will  cause 
the  cyanide  to  fly.  If  it  strikes  the  flesh,  it  produces  a 
bum,  which,  on  account  of  the  poisonous  nature  of  the 
chemical,  is  liable  to  be  very  sore,  but  by  avoiding  the 
presence  of  any  form  of  moisture,  this  need  not  occur. 

Articles  made  of  malleable  iron,  as  cutters  for 
paper,  and  wood,  may  be  hardened  by  heating  in  this 
manner.  If  only  a  few  pieces  are  to  be  hardened,  the 
cyanide  may  be  heated  in  an  iron  dish  of  suitable  size, 
the  articles  suspended  in  the  dish  until  heated  suffi- 
ciently, when  they  may  be  quenched  in  a  bath  of  cold 
water,  or  warm  water,  according  to  the  nature  of  the 
work  to  be  done.  Should  this  prove  to  make  them 
too  hard,  a  bath  of  tallow  or  oil  may  be  used. 

Articles  made  of  machinery  steel  may  be  heated  in 
the  cyanide  crucible  for  hardening,  the  amount  of 
hardness  and  depth  which  it  penetrates  depending  on 
the  amount  of  heat  given  and  the  length  of  time  the 
article  is  left  in  the  cyanide. 

If  the  articles  are  of  a  size  that  warrants  it,  they 
may  be  suspended  in  the  cyanide  by  means  of  wires, 
as  previously  explained.     If  they  are  small  and  there 

no 


To  harden  throughout. 

are  many  of  them,  they  may  be  placed  in  baskets  made 
of  wire  cloth  and  suspended  in  the  molten  mass. 
These  baskets  should  not,  however,  be  made  of  gal- 
vanized wire,  or  have  any  solder  used  in  their  con- 
struction, or  the  articles  will  be  coated  with  lead. 
Care  must  be  exercised  when  placing-  the  articles  in  the 
basket,  not  to  put  in  too  many,  especially  if  the  basket 
is  to  be  dipped  into  the  hardening  bath,  as  the  pieces 
would  touch  each  other  when  in  the  water ;  consequently 
they  would  not  be  hard  at  these  points. 

When  it  is  desired  to  make  articles  other  than  cut- 
ting tools,  and  harden  them  throughout,  it  may  be 
done  by  procuring  a  low  grade  steel,  sufficiently  high 
in  carbon  to  produce  the  desired  result.  The  steel 
may  be  either  Bessemer  or  open  hearth.  If  hearth 
steel,  the  temper  must  be  suited  to  the  particular  pur- 
pose it  is  to  be  used  for.  When  the  article  is  ready  for 
hardening,  it  may  be  suspended  in  the  molten  cyanide ; 
when  it  has  heated  for  a  sufficient  length  of  time,  it  is 
removed  and  plunged  in  the  bath.  If  hardness  is  the 
only  quality  desired,  use  a  bath  of  water.  If  a  hard 
surface  is  desired,  and  a  very  tough,  strong  interior, 
use  a  bath  of  oil  and  tallow. 

Malleable  iron  may  be  hardened  by  heating  in 
cyanide  of  potassium,  as  is  the  case  with  machinery 
steel,  the  depth  of  hardening  depending  on  the  length 
of  time  it  was  left  in  the  cyanide.  If  colors  are  desired, 
the  surfaces  must  be  polished,  and  a  bath  of  clean 
water  used.  If  a  strong,  tough  effect  is  desired, 
quench  in  oil. 

It  is  sometimes  desirable  to  color  a  piece  of  work 
in  imitation  of  case  hardening,  yet  leaving  the  article 
soft.     If  the  piece  is  made  of  machinery  steel  of  low 


Uniform  heat  necessary  to  hardening. 

carbon,  or  of  malleable  iron,  this  is  accomplished  by 
using  a  cyanide  made  especially  for  the  purpose.  This 
is  known  as  **  50  per  cent,  fused  cyanide  of  potassium." 

Hardening  Steel. 


CO 

Having  considered  the  nature  of  steel,  methods  of 
heating  for  different  purposes,  and  the  means  of  cooling 
by  the  various  baths,  we  will  proceed  to  the  considera- 
tion of  hardening  articles  of  various  types.  As  it  would 
be  impossible  to  consider  all  the  articles  that  require 
hardening  in  the  various  shops  throughout  the  country, 
such  examples  have  been  selected  as  are  representative 
of  the  articles  that  are  commonly  hardened. 

Uniform  heats  are  the  secret  of  success  when  hard- 
ening steel.  A  greater  part  of  the  trouble  experienced 
by  men  not  skillful  in  this  branch  of  the  business  arises 
from  this  fact  not  being  observed.  The  writer  cannot 
resist  the  desire  to  caution  the  reader  against  trouble 
arising  from  this  cause,  and  hopes  he  will  be  pardoned 
if  he  apparently  repeats  this  warning  oftener  than  may 
seem  necessary. 

When  hardening  steel,  avoid  too  rapid  cooling  of 
the  surface,  as  it  is  then  rigid  and  inflexible,  while  the 
inside  of  the  piece  is  still  undergoing  the  change  in 
structure  incident  to  hardening.  As  a  consequence,  if 
the  outer  surface  is  hard  and  inflexible,  and  the  internal 
portion  is  undergoing  changes  in  size  and  structure,  the 
outer  surface  will  crack  from  the  enormous  strain 
brought  to  bear  on  it.     It  is  advisable  when  hardening 


How  to  heat  to  avoid  strains. 

small  articles  to  heat  the  contents  of  the  bath  somewhat, 
to  avoid  the  sudden  cooling  mentioned. 

As  stated,  when  the  surface  becomes  hard  before 
the  center  has  ceased  changing  its  size  and  structure, 
there  is  a  tendency  to  crack  the  surface  from  the  in- 
ternal strains. 

To  overcome  this  tendency,  the  piece  should  be 
heated  to  a  degree  that  allows  the  surface  to  yield  some- 
what and  conform  to  the  strains  in  the  piece.  The 
amount  of  heat  necessary  to  produce  this  result  has 
been  ascertained 
to  be  at  the  tem- 
perature of  boil- 
ing water  (212  de- 
grees). An  ex- 
perienced hard- 
ener can  deter, 
mine  the  necessary 
amount  of  heat 
very  nicely  by  the 
sense  of  feeling, 
heat  the  steel  until, 
when  touched  with 
the  moistened 
finger,  the  peculiar 
snapping  sound  is 
heard.  This  is  the 
same  as  the  house- 


r 


Perforated  Catch  Pan 


Y<'^<'<'^<'<'<'<'^<'i^///////<'^<'?<'///^?<'<'<'<'<'<'<'?<'i'/<^ 


i 


=3^ 


The  Derry  Collard  Co. 


Figure  45.      Bath  for  hardening  in  hot  water. 


wife  tells  when  her  irons   have  reached  the  proper 
temperature  for  ironing  linen. 

When  pieces  are  hardened  in  large  quantities,  it 
becomes  very  costly  practice  reheating  each  piece  over 
the  fire,  guaging  the  heat  by  the  sense  of  feeling.     A 


13 


Cold  baths  not  usually  advisable. 

good  plan  in  such  cases  is  to  have  a  tank  of  the  descrip- 
tion shown  in  Fig.  24.  A  steam  pipe  is  connected  with 
the  tank,  as  by  this  means  it  is  possible  to  heat  the 
water  to  any  desired  degree  to  the  boiling  point.  A 
perforated  pan  is  provided  to  catch  the  work  as  it  is 
dropped  into  the  tank.  Occasionally  the  pan  may  be 
removed  from  the  tank  by  means  of  the  wires  shown, 
the  pieces  emptied  out  and  the  pan  returned. 

As  the  pieces  are  removed  from  the  hardening  bath, 
they  may  be  dropped  into  this  tank,  and  the  tendency 
to  crack  overcome.  For  certain  articles  the  brittleness 
is  reduced  sufficiently,  making  it  unnecessary  to  draw 
the  temper  any  more. 

The  use  of  extremely  cold  baths  is  not  as  a  rule 
advisable.  Results  fully  as  satisfactory  so  far  as  the 
hardened  surface  is  concerned,  are  obtained  if  th-e  bath 
is  warmed  somewhat,  and  the  danger  of  cracking  is 
greatly  reduced. 

It  is  claimed  that  when  articles  made  of  steel  and 
heated  red-hot  are  plunged  in  a  cooling  bath,  the  out- 
side surface  becoming  chilled  and  consequently  con- 
tracted, causes  by  this  process  of  contraction  an 
immense  pressure  on  the  internal  portion  of  the  steel 
which  is  red-hot ;  this  pressure  has  the  effect  of  raising 
the  temperature  of  the  interior  of  the  steel  still  higher, 
with  the  result  that  it  expands  still  more.  This  extra 
expansion  is,  of  course,  communicated  to  the  hardened 
(and  consequently  unyielding)  surface,  and  this  being 
unable  to  stand  the  immense  strain,  either  cracks  or 
bursts. 

If  the  contents  of  the  bath  are  heated  to  some 
extent,  the  surface  is  not  chilled  below  a  temperature 
that  allows  it  to  yield  somewhat,  allowing  it  to  con- 

114 


How  to  straighten  hardened  work. 


form  in  a  measure  to  the  internal  pressure,  which  is 
relieved  as  that  portion  cools  and  contracts. 

The  pliability  of  steel  when  warmed  is  illustrated 
in  the  case  of  such  tools  as  taps,  reamers,  or  drills, 
which  become  crooked  when  hardening.  In  order  to 
straighten,  it  is  necessary  to  apply  a  certain  amount 
of  heat.  Place  the  tool  between  the  centers  of  a 
lathe,  with  the  convex  side  toward  the  operator,  a 
piece  of  stock 
is  then  put  in 
the  tool  post 
of  the  lathe, 
having  one 
end  against 
the  bowed 
side,   as  shown 


Figure  46. 
Method  of  straight- 
ening work  bent 
in  hardening. 


Fig.  46. 
The  article  is  now  heated 
until  oil  placed  on  the  sur- 
face commences  to  smoke; 
pressure  is  applied  by  means 

of  the  cross  feed  screw  and  until  the  article  is  slightly 
bowing  in  the  opposite  direction. 

The  piece  should  now  be  suddenly  cooled  while  in 
this  position.  If  it  is  not  straight,  the  process  should 
be  repeated.  Now,  it  is  safe  to  spring  the  steel  when 
warm,  but  when  it  is  cooled,  even  after  heating,  as  de- 
scribed, it  will  break  if  any  great  amount  of  pressure 
is  applied.  Should  it  spring  somewhat  when  cold,  it 
will  return  to  its  original  shape  when  the  pressure  is 
removed,  thus  proving  that  hardened  steel,  when 
heated  to  a  certain  degree,  is  somewhat  pliable.  It  is 
for  this  reason  the  surface  of  a  hardened  piece  is 
reheated  to  **  remove  strains,"  as  it  is  familiary  termed, 

"5 


Drawing  the  temper. 

or  it  is  made  pliable  by  heat,  and  in  this  condition  con- 
forms to  the  immense  strain  incident  to  hardening. 

In  the  case  of  the  article  heated  and  straightened 
by  pressure,  it  is  necessary  to  cool  the  piece  uniformly. 
Should  one  side  be  cooled  and  the  opposite  side  left 
hot,  the  piece  would  probably  crack  from  the  unequal 
contraction.  By  carefully  following  this  plan  it  will  be 
possible  to  save  many  tools  that  would  otherwise  have 
to  be  thrown  away — or  which,  if  used,  would  not  be 
satisfactory. 


Drawing  the  Temper 
after  Hardening. 


CO 

When  a  piece  of  steel  is  hardened  it  becomes  brit- 
tle. When  the  design  of  the  piece  is  such  that  the 
working  surface  has  sufficient  backing,  it  is  safe  and 
advisable  to  keep  the  article  as  hard  as  when  it  comes 
from  the  bath.  But  in  the  case  of  tools  having  slender 
cutting  edges,  as  taps,  screw  threading  dies  and  mill- 
ing machine  cutters  of  the  ordinary  styles,  it  becomes 
necessary  to  reduce  the  amount  of  brittleness  in  order 
that  it  may  stand  up  when  in  use.  This  is  done  by  re- 
heating the  piece  somewhat. 

The  process  of  reheating  also  has  the  effect  of  soft- 
ening the  steel  to  a  considerable  degree.  It  is  not  gen- 
erally desirable  to  soften  it,  but  it  is  necessary  to  do  so  in 

ii6 


The  amount  of  heat  necessary  to  temper. 

order  to  reduce  the  brittleness.  This  reheating  is  gener- 
ally termed  "drawing  the  temper."  Unfortunately, 
the  word  temper  is  understood  as  having  more  than  one 
meaning,  and  as  a  consequence  people  are  sometimes 
puzzled  to  know  exactly  what  one  means  when  the  term 
is  used.  By  some  it  is  understood  as  the  double  pro- 
cess of  hardening  and  drawing  the  temper.  To  others 
it  simply  conveys  the  idea  of  drawing  the  temper  of  a 
hardened  piece,  and  will  be  so  used  by  the  writer  in 
connection  with  treating  steel  by  heat,  although  the 
steel  maker's  definition  of  the  word  temper  will  be  used 
occasionally  to  designate  the  percentage  of  carbon  the 
steel  contains. 

When  steel  is  heated,  the  amount  of  heat  it  absorbs 
may  be  determined  by  the  surface  colors,  provided  it 
has  been  brightened  previous  to  heating.  It  is  custom- 
ary after  hardening  to  brighten  the  surface  with  a  stick 
whose  surface  has  been  coated  with  glue  arid  then  cov- 
ered with  emery,  or  a  piece  of  emery  cloth  may  be 
attached  to  a  stick  or  held  on  a  file.  After  brightening, 
the  piece  may  be  subjected  to  heat.  As  the  steel  be- 
comes heated  various  colors  will  appear  on  the  bright- 
ened surfaces.  The  first  color  visible  is  a  faint  straw 
color,  then  straw  color,  light  brown,  darker  brown, 
brown  with  purple,  light  blue,  darker  blue.  If  heated 
to  a  black,  the  hardness  is  reduced  to  a  point  that 
makes  the  steel  practically  soft. 

The  amount  of  heat  necessary  to  give  steel  in 
tempering,  depends  on  the  make  of  the  steel,  how  hot 
it  was  heated  when  hardening,  and  for  what  purpose  it 
is  to  be  used.  The  method  ordinarily  practiced  has 
been  briefly  described  above. 

When  work  is  done  in  large  quantities,  the  temper 
117 


Methods  of  drawing  temper. 

is  sometimes  drawn  by  placing  the  articles  in  a  pan 
having  a  long  handle,  as  shown  in  Fig.  47.  A  quantity 
of  clean  sand  is  put  in  and  the  pan  held  over  a  fire, 
moving  it  back  and  forth,  thus  keeping  the  sand  and 
work  in  motion.  The  surface  colors  can  be  closely 
watched  and  excellent  results  obtained.  If  there  are 
any  sharp  edges  or  cutting  teeth  that  will  be  harmed 
by  striking  against  the  other  pieces,  it  is  not  advisable 
to  use  this  method  unless  extreme  care  is  exercised, 
but  a  pan  of  sand  may  be  placed  over  the  fire  and  a 
few  pieces  of  work,  having  edges  as  described,  placed 
in  it  and  kept  in  motion  by  a  stick,  being  careful  not 
to  hit  them  together. 

An  excellent  furnace,  which  is  illustrated  in  Fig. 


The  Derry  CoUard  Co. 

Figure  47.      Pan  for  drawing  temper. 


48,  can  be  procured,  which  gives  very  satisfactory 
results.  The  pieces  to  be  tempered  are  placed  in  the 
pans,  D  D,  which  rotate  at  the  speed  of  two  or  three 
revolutions  per  minute,  the  pans  being  hung  loosely 
from  rods  connected  with  spokes  around  the  driving 
block  in  the  center,  which  receives  motion  from  the 
worm  and  gear,  A  B,  connected  with  power.  The 
door,  C,  is  closed  and  the  furnace  is  charged  with 
work,  and  may  be  opened  for  observation.  When 
opened,  the  door  forms  a  shelf  or  rest  for  the  pans. 

Xlg 


Revolving  furnace  for  tempering. 


The  thermometer  indicates  a  degree  of  temper  some- 
what different  from  the  actual  heat  in  the  furnace,  but 
if  the  temperature  indi- 
cated is  observed  when 
the  desired  temper  is  ob- 
tained, the  operation  may 
be  repeated 
with  satisfac- 
tory results. 

This  furnace 
is  designed  for 
tempering  small 
articles,  but  the 
writer  has  used 
it  with  excel- 
lent results  on 
punches  used 
for  punching 
rectangular 
holes  2  inches 
by  ^  inch,  the 
shanks  being 
i^  inches  in 
diameter  and  5 
inches  long. 
The  action  of 
the  furnace  de- 
pends  on   the 

heated  air,  with  Figure  48.     Revolving  furnace  for 

temperature    so  tempering  small  pieces. 

regulated  that  articles  of  irregular  shape  can  be  exposed 
to  it  long  enough  to  impart  the  proper  temper  to  the 
heavier  parts  without  drawing  the  temper  too  low  on 


119 


Tempering  lathe  tools. 


the  lighter  parts  of  the  same  piece.  By  means  fur- 
nished of  regulating  the  heat  generated,  the  injection 
of  the  heat  evenly  throughout  the  furnace  is  easily 
secured,  and  the  overheating  of  any  part  of  the  piece 
prevented. 

A  common  method  when  drawing  the  temper  of 
articles  which  are  of  a  uniform  thickness,  is  to  heat  a 
flat  piece  of  iron  to  a  red  heat,  lay  the  pieces  on  this, 
moving  them  around  and  turning 
them  over  occasionally  to  insure 
uniform  heating.  When  the  desired 
temper  color  shows,  the  piece  is 
immediately  immersed  in  oil  to 
prevent  its  softening  more 
than  is  desired. 
This  method  is 
open  to  objec- 
tions when  arti- 
cles  having 
heavy  and  light 
portions,  which 
must  be  heated 
alike,  are  to  be 
tempered,  be- 
cause the  lighter 
parts,  heating 
more  quickly  than  the  heavy  ones,  will  become  too  soft 
before  the  heavier  portions  reach  the  desired  temper. 

When  tools  having  heavy  parts  adjoining  the  cut- 
ting portion  are  to  be  hardened,  and  it  is  not  necessary 
to  harden  the  heavy  parts,  as  a  diamond  point  lathe 
tool  or  similar  article,  it  is  the  general  practice  to  heat 
the  tool  for  a  distance  on  the  shank — say  as  far  back  as 


Figure  49. 


The  Derry  CoUard  Co. 


Hardening  a  diamond  pointed 
lathe  tool. 


Tempering  in  oil. 

the  dotted  line  in  Fig.  49 — to  a  red  heat.  Plunge  the 
cutting  blade  into  the  bath,  being  careful  not  to  dip  the 
portion  marked  a  into  the  bath.  Work  up  and  down  to 
prevent  a  water  line,  and  move  around  to  avoid  steam. 
When  the  cutting  part  is  sufficiently  hardened,  remove 
from  the  bath,  and  allow  the  heat  from 
the  heavy  portion  to  run  into  the 
hardened  part  until  the  desired  color 
shows,  when  it  may  be  quenched  to 
prevent  its  running  any  lower. 

When  work  is  tem- 
pered in  large  batches, 
a  very  satisfactory 
method  consists  in  put- 
ting the  articles  in  oil 
and  heating  to  a  proper 
degree,  gauging  the 
heat  by  means  of  a 
thermometer. 

A  very  satisfactory 
tempering  furnace  is 
shown  in  Fig.  50.  Illu- 
minating gas  is  used  as 
fuel.  The  burning  gas 
circulates  around  the 
kettle  holding  the  oil, 
thus    heating    it    very 


Figure  50.     Oil  tempering  furnace. 


uniformly.  The  work  is  held  in  a  perforated  pail  or 
basket,  somewhat  smaller  than  the  inside  of  the  kettle. 
The  degree  of  heat  to  which  the  oil  is  brought  is 
shown  by  the  thermometer. 

If  not  situated  so  that  a  furnace  of  this  kind  is 
accessible,  a  kettle  may  be  placed  on  a  fire  in  a  black- 


121 


Oil  tempering  in  a  kettle. 

smith's  forge  and  built  up  around  with  bricks,  leaving 
a  space  up  around  the  kettle  for  coals.  Now  fill  the 
space  with  charcoal.  As  this  catches  fire,  it  heats  the 
oil  in  the  kettle.  The  articles  to  be  tempered  may  be 
placed  in  the  perforated  sheet  iron  pail,  at  least  two 
inches  smaller  than  the  inside  of  the  kettle.  The  pail 
should  have  a  flange  at  the  bottom,  as  shown  in  Fig. 


o   o  o  o  o    o 
o  o   o  o  o  o  o 
o  o  c  o  o  o  o 
ooooooooj 
oooooooo 
oooooooci 

lOOOOOOOC 


to  o  o  o  o  o  o  o  Oi 


Perforated  Pail 


Figure  51.     Oil  tempering  In  a  kettle. 


51,  or  it  should  be  blocked  up  i^  inches  or  2  inches 
from  the  bottom  of  the  kettle,  to  allow  the  oil  to  cir- 
culate freely  beneath  it. 

If  the  pail  were  to  rest  directly  on  the  bottom,  the 
pieces  of  work  at  the  bottom  of  the  pail  would  soften 
too  much  from  coming  in  contact  with  the  kettle, 
which  is  acted  on  by  the  direct  heat  of  the  fire.  The 
thermometer  should  be  placed  between  the  pail  and  the 


Temperature  of  temper  colors. 

kettle,  as  shown.  It  is  advisable  to  stir  the  oil  in  the 
kettle  occasionally,  in  order  to  equalize  the  heat. 
When  the  thermometer  shows  the  desired  degree  of 
heat,  the  pail  containing  the  work  may  be  removed, 
set  to  one  side,  where  no  current  of  air  can  strike  it, 
and  allowed  to  cool  off. 

When  pieces  of  hardened  steel  are  placed  in  a 
kettle  of  oil  and  heated,  the  temper  colors  do  not  show, 
so  it  becomes  necessary  to  gauge  the  heat  by  a  thermo- 
meter. The  temper  colors  are  significant  of  a  certain 
amount  of  heat  which  the  steel  has  absorbed. 

Faint  straw  color 430  degrees  Fahr. 

Straw   color 460       "  " 

Light  brown. 490 

Darker  brown 500 

Brown  with  purple  spots.  .510 

Light  purple 530 

Dark  purple 550 

Light  blue 570 

Darker  blue 600 

Blue,  tinged  with  green ...  630 


(( 


Knowing  the  proper  degree  of  heat  to  which  a 
piece  of  steel  should  be  subjected,  it  becomes  possible 
to  draw  the  temper  on  any  number  of  pieces  exactly 
alike,  and  much  more  uniformly  than  though  they  were 
gauged  by  color.  As  stated,  430  degrees  of  heat  repre- 
sents a  faint  straw  color,  while  460  degrees  a  full  straw, 
a  difference  of  only  30  degrees,  yet  when  tested  with  a 
file  by  one  accustomed  to  this  work,  there  is  a  vast 
difference  in  the  hardness  of  the  two.  While  the  differ- 
ence in  the  two  colors  is  slight,  yet  difference  in  the 
ability  of  the  tv/o  pieces  to  resist  wear  in  the  case  of 

123 


The  necessity  for  proper  temperatures. 

cutting  tools  is  quite  noticeable.  The  average  man 
does  not  detect  a  difference  of  lo  degrees  by  observing 
colors,  consequently  he  is  liable  to  have  a  product  vary- 
ing in  efficiency  if  he  attempts  to  draw  the  temper  by 
observing  the  color.  But  if  he  gauges  the  temper  by  a 
thermometer  he  can  get  his  product  within  a  limit  of  i 
degree  or  2  degrees  every  day,  and  at  a  much  less  cost 
than  if  he  were  to  draw  to  the  color,  provided  the  work 
is  done  in  large  quantities. 

At  times  a  tool  as  it  comes  from  the  bath  is  too 
brittle  to  stand  up  well,  yet  when  the  temper  is  drawn 
to  the  first  color  discernible,  /.  e. ,  a  light  straw — it  is 
too  soft  to  do  its  maximum  amount  of  work.  Now,  in 
a  case  of  this  kind  the  temper  may  be  drawn  to  200  to 
250  degrees,  or  any  temperature  that  proves  exactly 
right. 

The  writer  has  in  mind  tools  which,  if  left  dead 
hard,  would  crumble  away  on  certain  projections  when 
used;  but  if  they  were  heated  to  the  faintest  straw 
color,  would  not  do  the  amount  of  work  required  of 
them.  But  if  they  were  taken  from  the  hardening 
bath  and  placed  in  a  kettle  of  boiling  water  (212  de- 
grees) and  left  there  about  five  minutes,  would  show 
excellent  results  when  used.  Other  tools  showed  best 
results  when  heated  to  300  degrees  and  some  to  350 
degrees.  These  facts  are  given  the  reader  in  order 
that  he  may  understand  that  there  is  a  method  whereby 
the  amount  of  brittleness  in  a  piece  of  steel  may  be  re- 
duced to  a  point  where  it  will  stand  up  to  its  work  and 
yet  not  soften  it  as  much  as  is  necessary  when  it  is 
drawn  to  the  first  temper  color  discernible. 

The  colors  visible  on  the  brightened  surface  of  a 
piece  of  heated  steel  are  supposed  to  be  due  to  a  thin 

124 


Reasons  for  colors  on  brightened  surface. 

coating  of  oxide,  formed  by  the  action  of  the  air  on 
the  heated  surface.  If  a  piece  of  steel  is  heated  in  oil 
away  from  the  air,  these  colors  will  not  present  them- 
selves, provided  the  steel  is  left  in  the  oil  until  the 
temperature  is  below  the  point  necessary  to  show  the 
faint  straw  color  (430  degrees). 

It  is  necessary,  in  order  to  gauge  the  temper  to 
which  steel  is  drawn  if  gauged  by  temper  colors,  not 
only  to  have  the  piece  bright,  but  it  must  be  free  from 
grease  or  oil,  as  the  presence  of  oil  will  cause  the 
colors  to  show  differently  than  if  the  surface  were 
clean. 

It  is  the  custom  in  some  shops  to  polish  the 
hardened  pieces  and  then  draw  the  temper  leaving  the 
temper  color  as  a  finish.  Now,  if  the  work  has  been 
polished  on  a  greased  wheel,  a  certain  amount  of  the 
oil  is  taken  into  the  pores  of  the  steel.  When  it  is 
heated  in  tempering,  this  oil  comes  to  the  surface  of 
the  steel  and  produces  a  peculiar  appearance.  The 
surface  appears  streaked.  If  it  is  wiped  with  an  oily 
piece  of  waste  or  cloth,  this  streaky  or  mottled  look 
disappears.  Many  hardeners  always  wipe  a  piece  of 
steel  being  tempered  with  some  substance  having  oil 
or  vaseline  on  it ;  the  appearance  of  the  temper  color 
is  slightly  changed  by  so  doing,  but  allowance  is  made 
for  this. 

When  drawing  the  temper  of  articles  which  are 
small  or  thin,  it  is  not  advisable  to  heat  by  rapid 
methods,  heating  until  the  desired  color  appears  and 
then  quenching  in  cold  water  to  keep  it  from  running 
too  low.  The  cold  water,  on  account  of  the  sudden 
chill  which  it  gives  an  article  heated  to  430  to  500  or 
more  degrees,  has  a  tendency  to  make  it  more  brittle 

1*5 


Always  harden  at  the  lowest  heat. 

than  it  would  be  if  it  were  drawn  to  the  proper  temper 
color  and  allowed  to  cool  off  slowly,  or  plunged  in 
warm  oil  or  hot  water.  In  the  case  of  large,  heavy- 
pieces,  or  where  brittleness  would  do  no  particular 
harm,  this  precaution  need  not  be  observed  so  closely. 
But  on  the  other  hand,  if  brittleness  did  no  harm,  it 
would  not  be  necessary  to  draw  the  temper,  because 
few  tools  are  ever  too  hard  for  the  purpose  for  which 
they  are  intended.  For,  as  previously  explained,  the 
process  of  hardening  makes  them  too  brittle  to  stand 
up  well  when  they  are  in  use,  consequently  they  are 
tempered  to  reduce  the  brittleness  to  a  point  where 
they  will  stand  up.  But  the  process  of  tempering  is  also 
(unfortunately  for  cutting  tools)  a  process  of  softening. 

It  should  be  the  aim  of  the  hardener  at  all  times 
to  harden  steel  at  the  lowest  heat  that  will  give  the 
desired  result,  because  in  this  condition  the  steel  is  the 
strongest  possible,  and  consequently  will  not  need  the 
temper  drawn  as  much  as  though  it  was  given  a  higher 
heat  and  made  brittle.  Many  times  the  writer  has 
seen  hardeners  heat  a  diamond  point  turning  tool  to  a 
temperature  much  hotter  than  was  necessary  when 
hardening,  then  draw  it  to  a  full  straw  color  in  order 
to  reduce  the  brittleness  so  it  would  be  able  to  cut  and 
not  flake  off,  or  the  surface  cave  in  when  the  tool  was 
cutting. 

Now,  the  tool  in  this  condition  could  not  do  any- 
where near  its  maximum  work  in  a  given  time. 
Neither  would  the  life  of  the  tool  be  as  long  as  though 
it  were  hardened  at  the  proper  heat,  and  in  this  case  it 
is  doubtful  if  it  would  be  necessary  to  draw  the  temper 
at  all,  provided  it  had  not  been  improperly  heated 
when  forging.      Many  times  tools  of  this  description 

ia6 


Examples  of  hardening. 

can  have  the  temper  drawn  sufficiently  by  immersing 
the  tool  after  hardening  in  a  dish  of  boiling  water  and 
leaving  there  a  few  minutes. 


Examples  of  Hardening. 


CO 

When  hardening  articles  made  of  tool  steel,  it  is 
necessary  to  consider,  first,  the  nature  of  the  steel  used, 
the  construction  of  the  article,  next  the  shape  of  the 
article,  and  the  use  to  which  it  is  to  be  put.  It  is  also 
necessary  to  take  into  consideration  the  means  of  heat- 
ing furnished  by  the  shop,  and  the  bath  to  be  used  in 
quenching  the  article  after  it  is  heated. 

The  operator  should  adapt  himself  so  far  as  possi- 
ble to  circumstances  as  he  finds  them,  although  it  is  not 
advisable  to  attempt  the  impossible,  because  a  failure 
is  generally  counted  against  the  man  making  it,  rather 
than  to  any  lack  of  apparatus  necessary  to  do  a  job  suc- 
cessfully. By  this  is  meant  that  it  is  not  policy  to  at- 
tempt to  heat  a  piece  of  steel  for  hardening  in  a  fire 
that  cannot  be  made  to  heat  the  piece  the  entire  length 
under  any  conditions — that  is,  if  it  is  necessary  to 
harden  it  the  entire  length — ^because  such  an  attempt 
must  end  in  a  manner  disastrous  to  the  steel.  It  is, 
however,  the  best  plan  to  attempt  to  find  some  means 
whereby  the  piece  may  be  heated  properly  by  means 
of  the  apparatus  at  hand. 

The  writer  remembers,  when  a  boy,  seeing  a  tool 

117 


How  a  long  reamer  was  heated. 

maker  heating  a  long  taper  reamer.  The  only  means 
of  heating  furnished  by  the  shop  was  an  ordinary  black- 
smith's forge.  By  building  a  large,  high  fire  he  was 
not  able  to  do  a  job  satisfactory  to  himself,  so  he  cleaned 
the  fire  out  of  the  forge,  and  then  took  some  fire  brick, 


Figure  52.      How  a  long  reamer 
was  heated. 


The  Deny  Collard  Co, 


placing  two  rows  on  the  forge,  as  shown  in  Fig.  52. 
On  these  he  placed  pieces  of  wire,  about  one-half  inch 
apart,  built  two  rows  of  bricks  on  top  as  shown,  thus 
forming  an  oven,  and  then  built  a  fire  of  charcoal  on 
the  wires  between  the  bricks.  By  standing  bricks  up 
at  the  openings  at  the  ends,  he  was  enabled  to  get  a 
very  good  fire  in  which  he  heated  the  reamer  in  a  very 
satisfactory  manner. 

While  it  would  not  have  been  wise  to  have  pursued 
this  method  of  heating,  if  there  had  been  many  pieces 
of  the  kind  mentioned  to  be  hardened,  yet  the  fact  that 
this  man  was  able  to  adapt  himself  to  circumstances 
and  devise  a  way  of  doing  a  seemingly  impossible 
thing,  made  him  a  valuable  man  in  the  estimation  of 
his  employers.     It  is  the  man  who  can  do  the  seem- 

128 


The  preference  of  some  hardeners. 

ingly  impossible  things  about  a  shop  that  is  looked 
upon  as  the  invaluable  man,  and  it  generally  counts, 
as  would  be  seen  if  his  pay  envelope  was  examined. 

While  it  is  advisable,  whenever  possible,  to  study 
up  some  way  of  doing  the  work,  do  not  attempt  the 
impossible  unless  some  one  over  you  in  authority 
assumes  the  responsibility.  It  is  better  to  acknowledge 
your  lack  of  ability  than  to  spoil  a  costly  piece  of  work, 
when  it  would  have  been  considered  advisable  by  those 
in  authority  to  have  sent  the  article  to  some  one  having 
the  necessary  equipment,  had  their  attention  been 
called  to  the  matter. 

Cases  like  this  may  often  be  used  to  good  advan- 
tage in  pointing  out  the  advisability  of  securing  better 
facilities  for  hardening  and  tempering.  As  long  as  it 
is  possible  to  get  along  without  any  equipment  but  a 
common  blacksmith's  fire,  it  is  often  very  hard  to 
obtain  anything  better. 


Hardening   Dies. 


If  it  is  necessary  to  heat  a  large  die  in  an 
ordinary  blacksmith's  forge,  it  can  be  done.  It  is 
done  right  along  by  men  who  have  had  years  of  ex- 
perience, and  very  satisfactory  results  are  obtained. 
The  writer  knows  a  man  who  is  considered  a  very  suc- 
cessful hardener.  He  does  very  little  else  but  harden- 
ing large  drop  forging  dies.  He  heats  them  in  an  open 
fire  and  has  very  good  success.  He  could  have,  were 
he  to  ask  for  it,  the  very  best  equipment  that  money 
could  buy,  but  he  prefers  heating  by  the  method  men- 
tioned. 

The  writer  also  knows  of  an  old  man  who  lives 

129 


Poor  scheme  to  heat  in  blacksmith's  forge. 

four  or  five  miles  from  the  city.  The  electric  cars  run 
within  five  hundred  feet  of  his  house,  but  rather  than 
ride  on  **  them  air  new  f angled  devil's  contraptions," 
as  he  calls  them,  he  walks  to  the  city,  unless  some  of 
his  neighbors  give  him  a  ride  in  their  carriage.  It 
may  not  seem  to  be  a  parallel  case.  If  it  isn't,  the  odds 
are  in  favor  of  the  farmer,  as  there  may  be  a  certain 
danger  in  riding  in  the  trolley  cars. 

Now,  it  is  possible  to  heat  a  large  piece  of  steel, 
such  as  a  drop  forging  die,  in  a  blacksmith's  forge  by 
building  a  large,  high  fire  of  charcoal,  placing  the  die 
on  this,  making  certain  that  the  face  is  buried  in  the 
live  coals  to  a  depth  of  several  inches.  It  would  be 
necessary  to  raise  the  die  occasionally  and  work  the 
coals  under  it,  as  it  would  not  do  to  allow  the  air  from 
the  blast  to  strike  the  face.  It  is  very  necessary  to 
heat  the  face  uniformly.  In  order  to  do  this  it  may  be 
found  necessary  to  move  the  die,  so  that  some  part 
that  is  heating  slowly  may  be  placed  in  a  position 
where  it  will  get  more  heat. 

Now,  while  it  is  possible  to  heat  work  of  the  descrip- 
tion mentioned  by  the  method  described,  it  is  not  policy 
to  do  it,  provided  any  other  means  is  at  hand,  or  can  be 
procured — that  is,  if  there  are  many  pieces  to  be  hard- 
ened. If  there  are  but  one  or  two  pieces,  it  is  possible 
by  using  extreme  care  to  get  good  results ;  but  if  there 
are  many  of  them  it  is  folly,  speaking  from  a  commer- 
cial standpoint,  to  heat  by  this  method. 

A  furnace  which  gives  very  good  results  may  be 
made,  if  it  is  not  considered  advisable  to  purchase  one 
especially  adapted  to  this  class  of  work.  Fig.  53  repre- 
sents a  muffle  furnace  burning  hard  coal  as  fuel, 
although  charcoal  or  coke  may  be  burned ;  but  it  will 

130 


"Home-made"  furnace  for  die  work. 

be  found  easier  to  maintain  a  uniform  heat  by  the  use 
of  hard  coal,  and  as  the  products  of  combustion  do  not 
come  in  contact  with  the  piece  being  heated,  they  cannot 
in  any  way  harm  it.  A  represents  the  muffle  which 
receives  the  work.     This  is  located  directly  over  the 


Figure  53. 


The  Dorry  Collard  Co. 

** Home-made"  furnace  for  die  work. 


fire  box  B.  The  heat  and  gas  from  the  fire  pass  up  the 
sides  and  back  of  the  muffle,  thus  insuring  a  very  strong 
heat.  The  ash  box  C  is  provided  with  a  door  which  has 
a  sliding  damper  to  furnish  a  draft  for  the  fire.  The 
smoke  pipe  is  connected  with  the  chimney.  This  is 
also  provided  with  a  damper  to  use  in  controlling  the  fire. 
The  die  may  be  blocked  up  from  the  bottom  by 

131 


r 


A 


Z 


■•:•• 


Boxes  for  heating  dies. 

means  of  several  pieces  of  iron  or  fire  brick  to  prevent 
the  face  coming  in  direct  contact  with  the  floor  of  the 
muifle.  The  door  of  the  muffle  should  have  an  open- 
ing, which  should  be  covered  with  a  piece  of  mica  in 
order  that  the  heat  may  be  readily  observed  without 
cooling  the  die. 

When  many  very  large,  heavy  dies  are  heated  it  is 
advisable  to  have  the  bottom  of  the  muffle  on  a  level 
with  the  floor, 
sinking  the  fire 
box  and  ash  box 
in  the  ground. 
By  having  the 
muffle  on  a  level 
with  the  floor 
it  is  not  neces- 
sary to  raise  the 
die  in  order  to 
get  it  into  the 
muffle.  When 
it  is  not  consid- 
ered  advisable 

to  do  this,  an  iron  platform  may  be  built  on  a  level 
with  the  bottom  of  the  muffle.  The  heated  die  may 
be  run  out  on  this  and  then  taken  with  tongs  or  grap- 
pling hook  and  carried  to  the  bath. 

Other  forms  of  furnaces  which  may  be  used  for 
this  purpose  are  illustrated  under  the  section  showing 
Methods  of  Heating. 

It  is  customary  with  some  manufacturers  who  make 
a  great  many  dies  to  harden  them  in  the  following  man- 
ner :  Take  a  box  2  or  3  inches  longer  and  wider  than 
the  die,  and  4  or  5  inches  deeper.     Put  in  about  2  inches 


^WZ/Z/Z/Av^'^^^^^ 


The  Derry  Collard  Co. 


Figure  54.     Box  for  heating  dies  in 
charred  leather. 


132 


Proper  methods  for  heating  dies. 

of  granulated  charred  leather,  place  the  face  of  the  die 
on  this,  as  shown  in  Fig.  54,  then  fill  the  box  with 
leather. 

Some  hardeners  use  a  box  large  enough  to  take  in 
the  whole  die  and  allow  for  a  cover  on  top.  It  is  then 
entirely  removed  from  the  action  of  the  fire,  even  if 
heated  in  a  furnace  where  the  work  is  placed  directly 
in  the  fire.  But  as  it  is  not  possible  to  get  a  test  wire 
down  through  the  center  of  the  die,  and  a  wire  at  the 
sides  of  the  die  would  not  show  the  amount  of  heat  the 
die  contained,  and  as  there  would  be  no  means  of 
observing  the  heat,  the  operator  would  have  no  means 
of  knowing  whether  the  die  was  too  hot  or  not  hot 
enough,  or  whether  it  was  heating  uniformly.  And  as 
the  decarbonization  of  the  surface  of  the  upper  part  of 
the  die  is  of  little  consequence,  the  plan  suggested  by 
Fig.  54  will  be  found  the  most  satisfactory,  as  the 
heats  can  be  watched  and  the  die  moved  occasionally 
in  order  to  equalize  the  heat,  which  is  apt  to  be  greater 
in  one  part  of  the  furnace  than  in  another.  The  furnace 
should  not  be  heated  much  above  the  temperature 
desired  for  the  die.  It  is  better  to  take  a  longer  time 
in  heating  than  to  heat  unevenly,  thereby  setting  up 
strains  which  are  bound  to  manifest  themselves  when 
a  piece  is  hardened,  or  if  they  do  not  at  that  time  they 
will  shortly  afterward. 

When  the  proper  heat  has  been  obtained,  the  box 
may  be  removed  from  the  furnace  and  the  die  taken 
out  and  plunged  into  the  bath.  The  form  of  bath 
used  for  this  class  of  work  differs,  some  hardeners  pre- 
ferring one  with  a  jet  of  water  coming  up  from  the 
bottom,  as  shown  in  Fig.  55.  This  works  very  nicely 
if  the  impressions  are  not  too  deep,  in  which  case  the 

133 


I 


L 


Die 


Bath  for  hardening  dies. 

steam  formed  has  a  tendency  to  rise  in  the  impressions 
and  keeps  the  water  from  going  to  the  bottom.  When 
dies  of  this  description  are  to  be  hardened,  a  bath  may 
be  constructed  with  an  overhead  pipe,  as  shown  in  Fig. 
56.  By  this  means  the  die  is  placed  on  the  rods  shown, 
and  when  the  water  is  turned  on  it  will  go  to  the  bot- 
tom of  any  im- 
pression  that 
would  be  likely 
to  be  in  any  die. 
This  form  has 
the  further  ad- 
vantage that  a 
cupful  of  strong 
solution  of  salt 
and  water,  pot- 
ash and  water, 
or  cyanide  of 
potash  and 
water  may  be 
dashed  on  the 
face  and  into 
the  impression 
just  ahead  of  the 
jet  of  water.  This  has  the  effect  of  starting  any  scale 
that  may  have  been  formed  after  the  die  was  exposed 
to  the  air. 

Some  hardeners  have  rods  in  the  bath  for  the  face 
of  the  die  to  rest  upon,  as  shown  in  Fig.  55,  then  allow 
the  jet  to  play  against  the  face,  while  others  claim  bet- 
ter results  if  the  die  is  worked  up  and  down  somewhat 
in  the  bath  as  described. 

It  is  customary  with  many  manufacturers  who 


Supply 


Ovecflaw 


Figure  55.      Bath  for  hardening  dies. 


»34 


Baths  for  hardening  dies. 

have  many  dies  of  this  character  to  harden,  to  use  a 
bath  having  an  inlet  pipe  coming  up  from  the  bottom, 
as  just  shown.  When  the  die  is  properly  heated, 
it  is  placed  on  the  rods  with  the  dovetailed  tongue 
down ;  the  stream  of  water  is  allowed  to  play  against 
this  side  of  the  die  until  it  is 
somewhat  cooled ;  this  not  only  (C>1 
prevents  this  portion  springing 
when  the  face  is  hardened,  but 
it  allows  the  heat  to  run  to  the 
face  of  the  die. 


/Imk 


Figure  56. 
Bath  for  hard- 
ening dies. 

After  the 
tongue  side  is 
sufficientl}'- 
cooled,  the  die 
is  turned  over 
and  the  stream 
of  water  is  di- 
rected against 
the  face;  the 
o  V  er  flo  w  is 
checked  suffi- 
ciently to  allow 
the  water  to 
rise    several 

inches  above  the  face,  on  the  sides  of  the  die ;  that  is, 
it  is  immersed  several  inches  in  the  bath;  the  depth 
of  immersion  depending  on  the  character  of  the  die  and 
the  custom  in  the  individual  shop. 

When  dipping  large,  heavy  dies  in  the  bath,  it  is 
advisable  to  hold  the  die  with  a  pair  of  grappling 
hooks,  as  shown  in  Fig.  57.  These  should  be  attached 
to  a  rope  or  chain  and  operated  by  a  pulley,  in  order 


The  Deny  Collard  Co. 


Overflow 


135 


Tongs  for  handling  heavy  dies. 


that  the  die  may  be  raised  and  lowered  somewhat  in 
the  bath.  Then  again,  it  would  not  be  advisable  for 
the  workman  to  dip  so  large  a  piece  of  steel  with  tongs 
that  necessitated  holding  his  hands  and  arms  over  the 
bath,  as  the  im-  ^^  Excellent   results 

mense  volume  of  vw/  may  be  had  by  the 

steam   would   be  //  \  ^^^  ^^  ^  furnace  built 

liable   to   burn  //      >\  expressly  for  this 

him;  neither  /^  \V\  class  of  work  (see 
could  he  properly  \  I  /  /  Fig.  58).  The  die  A 
support    the   die        \  \    /  I        is  supported  on  a 


in  the  bath. 


Figure  57. 

Tongs  for 

handling 

heavy  dies. 


platform  B,  and  is 
raised  mechan- 
ically, so  that 
the  amount 
which  it  is  nec- 
essary to  hard- 


en is  in  the  furnace,  while  the  rest  of  the  die  is  below 
and  removed  from  the  action  of  the  heat.  The  heat- 
ing chamber  is  on  top,  with  burners  entering  opposite 
sides  and  projecting  the  flame  against  the  top  lining 
and  distributing  it  evenly.  The  die  should  not  be 
placed  on  the  platform  until  the  furnace  is  evenly 
heated,  when  it  may  be  raised  by  means  of  the  lever 
D,  until  the  face  enters  the  furnace  the  desired  amount. 
The  face  of  the  die  can  be  observed  through  the  open- 

136 


Heating  dies  with  a  gas  furnace. 


ing-  C.     When  heated  to  the  desired  degree,  the  plat- 
form is  lowered,  the   die  withdrawn  and  quenched. 
The  weight  of  the  die  is  counterbalanced 
by  the  weight  shown,  which  can  be  shifted 
as  occasion  requires. 

Dies  used  in 
making  molds 
for  hard  rub- 
ber and  similar 
work,  whose 
faces  are  en- 
graved, may- 
be packed  as 
described  and 
represented  in 
Fig.  54,  and 
run  until  the 
required  heat 
is  attained. 
After  the  heat 
becomesequal- 
ized — /.  e.y  the 
same  through- 
out— the  die 
may  be  dipped 
in  the  bath  of 
brine,  using 
the  arrange- 
ment shown  in 

Fig.  57.  It  is  necessary  to  get  the  die  in  the  bath  as 
soon  as  possible  after  removing  from  the  packing 
material  in  order  to  prevent  oxidation  of  the  face 
containing  the  engraved  work. 


Figure  58.      Gas  furnace  for  heating  dies. 


137 


Punching  press  dies. 

Dies  for  punch  press  work,  especially  those  used 
for  blanking — that  is,  punching  blanks  from  sheet  or 
other  stock — occasion  a  vast  amount  of  trouble  in  many- 
shops  when  they  are  hardened.  Observation  has  led 
the  writer  to  believe  that  most  of  the  trouble  is  caused 
by  uneven  heats.  The  corners  and  edges  of  the  block 
and  the  edges  surrounding  the  openings  will  heat  much 
more  rapidly  than  the  balance  of  the  die  block  unless 
extreme  care  is  used. 

Before  putting  the  die  in  the  fire,  all  screw  and 
dowel  pin  holes  and  holes  for  guide  pins  (stops)  should 
be  filled  with  fire-clay,  mixed  with  water  to  the  consis- 
tency of  dough.  This  prevents  the  contents  of  the  bath 
entering  the  holes,  and  reduces  the  tendency  to  crack. 
The  die  should,  if  possible,  be  heated  in  a  muffle  fur- 
nace, not  heating  the  furnace  much,  if  any,  hotter  than 
the  desired  heat  for  the  die.  When  it  is  to  the  proper 
heat  and  uniform  throughout,  remove  from  the  fur- 
nace, catch  by  one  end  with  a  pair  of  tongs  and  lower 
into  a  bath  of  brine.  Swing  slowly  back  and  forth  in 
the  bath,  in  order  that  the  contents  of  the  bath  may 
pass  through  the  openings.  This  insures  the  harden- 
ing of  the  walls,  as  otherwise  the  steam  generated 
would  force  the  contents  of  the  bath  away  from  the  die 
until  it  had  cooled  to  a  point  where  it  would  not  harden. 
When  the  die  ceases  to  sing,  it  may  be  removed  and 
plunged  into  a  tank  of  oil. 

There  is  not  much  danger  of  a  die  cracking  when 
dipped  in  a  bath,  provided  it  was  annealed  after  the 
blank  had  been  machined  all  over  and  the  openings 
blocked  out  somewhere  near  to  shape.  But  it  is  ex- 
tremely essential  that  the  utmost  care  be  taken  when 
heating  for  hardening.     Be  sure  that  no  part  of  the  die 

138 


How  to  prevent  cracking  of  dies. 

block  is  heated  any  hotter  than  it  should  be.  The  heat 
must  be  uniform  throughout  the  piece.  If  the  shape  is 
one  that  betokens  trouble,  it  is  advisable  to  heat  the 
contents  of  the  bath  considerably.  Generally  speak- 
ing, it  is  not  advisable  to  use  an  extremely  cold  bath 
on  this  class  of  work. 

The  writer  prefers  using  a  tank  of  generous  pro- 
portions, so  the  contents  would  not  be  materially 
affected  by  the  heated  piece,  and  heating  the  liquid  to 
a  degree  that  does  away  with  any  tendency  to  crack 
the  piece.  An  excellent  method  to  prevent  the  ten- 
dency to  crack  from  internal  strains,  consists  in  placing 
the  die,  after  hardening,  in  a  kettle  of  boiling  water, 
keeping  the  die  in  the  water  at  this  temperature  for 
one  or  more  hours,  according  to  the  size  of  the  die. 

If  the  temper  is  to  be  drawn  immediately  after  the 
die  is  taken  from  the  bath,  a  flat  piece  of  cast  iron  or 
scrap  steel  may  be  heated  while  the  die  is  being  heated, 
and  quenched.  It  is  customary  with  some  hardeners 
to  heat  the  piece  red-hot.  Brighten  the  face  of  the 
die  and  lay  it  on  the  heated  iron.  The  die  should  be 
moved  around  on  the  heated  piece  and  turned  over 
occasionally  to  heat  both  sides  alike.  When  the  temper 
has  been  drawn  the  desired  amount,  the  die  may  be 
immersed  in  oil,  thus  preventing  the  temper  being 
drawn  too  much. 

While  it  is  the  custom  of  many  hardeners  to  heat 
the  drawing  plate  red-hot,  as  explained,  before  placing 
the  die  on  it,  the  writer  considers  it  better  practice  to 
heat  the  plate  somewhat^  leaving  it  over  an  open  fire. 
Place  the  die  on  the  plate  and  gradually  raise  the  heat. 
It  is  rather  rough  treatment  for  a  piece  of  unyielding 
hardened  steel  to  be  brought  in  direct  contact  with 

139 


Don*t  bring  steel  to  sudden  heat. 

extreme  heat,  and  is  liable  to  crack  the  surface  of  the 
steel  in  innumerable  places,  especially  if  the  operatoi 
is  not  thoroughly  experienced  in  this  line  of  work. 

The  amount  necessary  to  draw  the  temper  of  a 
blanking  die  depends  on  the  steel  used  in  its  construc- 
tion, the  temperature  it  was  heated  to  when  hardened, 
and  the  nature  of  the  work  to  be  performed  by  it. 

Generally  speaking,  it  is  advisable  to  refer  the 
matter  of  how  hard  the  die  or  punch  should  be  to  some 
one  familiar  with  the  requirements  of  the  work  to  be 
done.  In  some  cases  it  is  desirable  to  have  the  punch 
the  harder  of  the  two,  although,  generally  speaking,  the 
die  is  left  harder  than  the  punch.  In  some  shops,  the 
one  that  requires  the  greater  expense  in  making  is  left 
the  hardest,  in  order  that  it  may  be  the  least  injured  in 
case  they  strike  together  when  in  use.  In  such  cases 
it  is  necessary  to  draw  the  one  that  is  desired  softest 
considerable  lower  than  the  other. 

But  as  the  circumstances  must  govern  the  relative 
hardness  of  the  two,  no  hard  and  fast  rule  can  be  given. 

It  is  customary  to  draw  to  a  temperature  varying 
from  that  which  produces  a  faint  straw  color,  to  a 
brown  with  purple  spots. 

Probably  no  one  class  of  tools  used  in  machine 
shop  work  requires  greater  care  on  the  part  of  the 
hardener  than  the  hardening  and  tempering  of  punches 
and  dies ;  and  probably  no  class  of  tools  involves  a  wider 
range  of  methods  of  hardening  and  degrees  of  hardness 
essential  to  produce  desired  results  in  the  individual 
shop. 

The  hardener  who  is  desirous  of  giving  satisfac- 
tion will  study  the  conditions  in  the  shop  where  the 
tools  are  to  be  used.     He  will  also  consider  the  steel 

140 


Hardening  the  punch. 


used  in  the  construction  of  the  tools  and  the  nature  of 
the  stock  to  be  machined.  It  will  be  necessary  also  to 
get  the  experience  of  men  familiar  with  the  work  to  be 
done,  because  a  die  and  punch  hardened  and  tempered 
in  a  manner  that  insured  satisfaction  in  one  shop  would 
not  meet  the  requirements  in  some  other  shop. 

When  hardening  the  punch,  use  extreme  care  in 
heating.  If  the  punch  is  strong  and  is  to  be  used  for 
punching  comparatively  light  stock,  it  is  not  necessary 
to  harden  it  the  entire  length.  Take,  for  instance,  the 
punch  shown  in 
Fig.    59,    to    be 


used  for  punch- 
ing sheet  steel 
■^Q  inch  thick. 
This  will  work 
satisfactorily  if 
hardened  to 
the  dotted  line 
shown. 

When,  how- 
ever, it  is  neces- 
sary to  harden  a 
piercing  punch  of 
the  design  shown 
in  Fig.  60,  it  will 
be  found  neces- 
sary to  harden 
the  entire  length 
of  the  end  a^  if 
the  punch  is  to  be 
used  on  heavy 
stock.     Should 


J '  ■      = 


Figure  59.      Punch  for  ^  inch  steel  plates. 


) 


141 


Kind  of  steel  to  use  for  punches. 

the  hardness  extend  only  to  the  dotted  cross  line,  it 
would  buckle,  as  shown  in  Fig.  6i,  when  punching 
stock  as  thick  as  the  diameter  of  the  punch. 

When  making  punches  that  are  heavy  and  strong, 
and  which  must  retain  a  good  edge,  it  is  advisable  to 
use   a   steel   of    comparatively  high   carbon.     But  if 


Figure  60.      Piercing  punch  for  heavy  work. 

punches  are  made  of  the  form  shown  in  Fig.  60,  best 
results  will  follow  if  a  comparatively  low  carbon  steel 
is  used,  as  it  is  not  as  liable  to  crystallize  as  if  a  higher 


The  Derrjr  CoUard  Co. 


Figure  61.      Result  of  hardening  only  as  far  as  the  dotted  line, 
as  shown  in  Figure.  60. 

Steel  were  used.  As  a  rule,  drill  rod  does  not  give 
good  results  when  used  in  making  tools  of  this  de- 
scription. 

When  punches  are  sufficiently  strong,  it  is  advis- 
able to  apply  the  heat  at  the  shank  end  when  draw- 
ing the  temper.  A  block,  as  shown  in  Fig.  62,  having 
several  holes  a  trifle  larger  than  the  shanks  of  the 
punches  may  be  heated  red  hot  and  the  punches  placed 
in  these  holes.     When  the  desired  temper  color  is  visi- 

144 


How  to  heat  slender  punches. 

ble  at  the  cutting  end,  the  punch  may  be  taken  from 
the  block  and  dropped  in  oil  to  prevent  its  becoming 
too  soft.  The  upper  end  of  punch  will,  of  course,  be 
softer  than  the  cutting  end. 

When  a  long,  slender  punch,  of  the  design  shown 
in  Fig.  60,  is  to  be  tempered,  and  the  punch  is  to  be 


The  Derry  CoUard  Co. 

Figure  62.      Heating  block  for  tempering  long,  slender  punches. 


subjected  to  great  pressure,  it  must  be  hardened  the 
entire  length,  and  the  temper  drawn  equally  the  whole 
length.  This  can  be  accomplished  by  heating  in  a 
heating  machine  of  the  design  shown  in  Fig.  48,  or  the 
punches  may  be  placed  in  a  pan  containing  sand  and 
drawn  over  a  fire.  Or  they  may  be  placed  in  a  kettle 
of  hot  oil,  gauging  the  heat  by  means  of  a  thermometer. 

If  intended  for  piercing  a  heavy,  tough  stock,  they 
will  be  found  to  work  very  satisfactorily  if  drawn  to 
a  full  straw  color,  460°. 

Many  hardeners  and  others  look  askance  at  ther- 
mometers and  always  associate  them  with  theory 
rather  than  practice,  with  the  laboratory  rather  than 


143 


Forming  and  ring  dies. 

the  workshop.  In  reality  they  are  just  as  practical  a 
tool  as  a  steel  scale  or  a  micrometer,  and,  like  them, 
enable  us  to  measure  rather  than  to  guess. 

Forming  Dies. 

When  hardening  forming  dies  or  dies  for  compres- 
sion work,  if  a  great  amount  of  pressure  is  to  be  exert- 
ed in  order  to  perform  the  necessary  work,  the  dies  will 
not  stand  up  as  well  if  hardened  at  a  low  heat  as  though 
heated  somewhat  hotter.  The  outside  surface  will  be 
hard,  but  under  pressure  this  surface  will  be  forced  or 
crushed  in,  the  interior  not  being  hard  enough  to  resist 
the  pressure  on  the  outer  surface.  It  is,  as  stated, 
sometimes  necessary  in  such  cases,  to  heat  the  block 
somewhat  hotter  than  if  it  were  a  cutting  tool,  yet  care 
must  be  exercised  that  the  piece  be  not  overheated. 
But  while  it  may  be  advisable  to  heat  somewhat  hotter 
than  is  the  case  with  most  tools,  the  heat  must  be  uni- 
form throughout  the  die. 

It  is  not,  generally  speaking,  advisable  to  draw  the 
temper  very  much  on  tools  of  this  description,  but  it  is 
necessary  to  remove  the  tendency  to  crack  from  in- 
ternal strains.  This  is  done  by  heating  the  die  over  a 
fire  until  it  is  at  a  temperature  that  makes  it  impossible 
to  hold  the  hand  on  it,  yet  not  hot  enough  to  percep- 
tibly start  the  temper,  or  it  may  be  boiled  in  a  kettle 
of  water  for  several  hours. 

Ring  Dies. 

When  hardening  large  ring  dies  or  pieces  of  a  cir- 
cular shape,  whose  size  and  weight  make  it  impracti- 

144 


Furnace  for  ring  dies. 

cable  to  harden  by  ordinary  methods,  it  is  a  good  plan 
to  heat  in  a  furnace  made  especially  for  this  class  of 
work.  Such  a  furnace  is  seen  in  Fig. 
63,  which  shows  a  circular  block  A  in 
position  for  heating.  It  is  resting  on 
strips  of  iron  C  supported  by  pieces 
of  fire-clay  B.  The  circular  piece  be- 
ing heated  should  be  in  the  center 
of  the  furnace — i.  e.y  evenly  dis- 
tant from  the  inner 
walls.  The  cover  D 
is  attached  to 
the  mecha- 
nism for  rais- 
ing the  cover, 
and  held  by 
the  chains  EE. 
It  is  possible, 
by  using  prop- 
er care,  to  heat 
work  very  uni- 
formly  in  a 
furnace  of  this 
description. 

A  method 
the  writer  has 
used  with  ex- 
cellent results 
when   harden- 
ing work  of  this   character,   consists   in  placing  the 
ring  or  circular  die  in  an  iron  box  two  or  three  inches 
larger  each  way  inside  than  the  circular  piece.     A  cir- 
cular box  gives  better  results  than  a  square  one,  as 


The  Ocrry  ColUird  ( 


Figure  63.      Gas  furnace  for  ring  dies 
and  similar  work. 


»4S 


Box  for  heating  ring  dies. 


Figure  64. 

Method  of  removing  ring 

dies  when  heated 

in  boxes. 


more  uniform  heats  may  be  obtained.  Place  i>^ 
inches  of  a  mixture  of  equal  parts  granulated  charred 
leather  and  charcoal  in  the  bottom  of  the  box.  Place 
the  piece  of  work  on  this,  cover  with  the  mixture 
to  a  depth  of  an  inch  or  so,  put  the  cover  on  the  box 
and  place  in  the  furnace. 

When  the  piece  is  of  a  uniform  red  heat,  the  box 
may  be  removed  from  the  furnace  and  the  piece  of 

work  taken  out  by 
grasping  it  with 
tongs  on  opposite 
sides,  as  shown  in 
Fig.  64.  Place  it 
on  a  device  which 
consists  of  a  ring 
having  three  han- 
dles, as  represented 
in  Fig.  65.  Have 
the  ring  (which 
should  be  made  of 
iron  or  machinery 
steel)  considerably 
thinner  than  the 
thickness  of  the  piece  to  be  hardened,  but  wide  enough 
to  screw  the  handles  in  as  shown.  The  handles  b  b 
are  threaded  on  one  end  and  bent;  they  are  then 
screwed  into  the  ring,  as  shown.  A  stud  c  having  a 
tapped  hole  is  screwed  in  also.  The  third  handle  is 
screwed  into  this.  The  object  of  making  it  by  this 
method  is,  the  handle  may  be  unscrewed  from  the  stud 
c  and  the  piece  to  be  hardened  put  in  place.  The 
handle  may  then  be  screwed  into  the  hole  in  stud.  If 
the  piece  of  work  is  very  large  and  heavy,  a  man  may 

146 


Device  for  handling  large  ring  dies. 

be  stationed  at  each  handle.  If  not  very  heavy,  two 
men  can  handle  it  all  right.  The  operators  should 
protect  their  hands  and  arms  in  some  manner  to  pre- 
vent being  burned  by  the  steam  generated  when  the 
red  hot  piece  comes  in  contact  with  the  water. 

It  will  be  necessary  to  use  a  bath  having  a  jet  of 
water  coming  up  from  the  bottom,  so  as  to  cool  quick- 
ly,  when    harden- 
,b  ing  work   of   this 

description.  Be- 
fore immersing, 
the  water  should 
be  turned  on,  and 
at  the  minute  the 
piece  is  dipped,  a 
quantity  of  table 
salt  (about  a  pint) 
should  be  thrown 
into  the  water. 
The  ring  should  be 
worked  up  and 
down  in  the  bath. 
When  the  *  *  sing- 
ing" ceases,  the 
supply  valve  may  be  closed.  The  water  in  the  bath 
may  become  somewhat  warm,  but  it  will  reduce  the  lia- 
bility of  cracking.  As  soon  as  the  piece  of  work  is 
reduced  to  the  temperature  of  the  bath,  it  may  be  re- 
moved, placed  over  a  fire  and  heated  to  prevent  crack- 
ing from  internal  strains.  If  it  is  necessary  to  draw 
the  temper,  the  piece  of  steel  may  be  brightened  while 
heating  and  the  temper  drawn  at  this  time. 

It  is  advisable  when  drawing  the  temper  of  articles 


Th*  Denry  ColUrd  Co. 


«47 


Forms  of  screw  cutting  dies. 

of  this  description  to  heat  very  slowly^  so  as  to  have  all 
parts  of  an  equal  temperature.  If  possible,  have  the 
heat  so  uniform  that  it  will  not  be  necessary  to  quench 
the  article  when  the  desired  heat  is  reached.  Should 
the  temper  colors,  however,  run  so  fast  that  it  seems 
necessary  to  quench  in  order  to  keep  it  from  becoming 
too  soft,  it  should  be  dipped  in  oil  or  hot  water,  as,  if 
dipped  in  cold  water,  it  would  have  a  tendency  to  cause 
brittleness. 

Screw  Threading  Dies. 

There  are  several  forms  of  the  die  under  considera- 
tion. They  are  sometimes  made  square,  then  again 
they  are  made  round  in  shape,  with  no  means  of  ad- 
justment. They  are  then  termed  solid  dies.  Most 
square  dies  are  made  solid. 


The  Derry  OoUard  Co. 
Figure  66.     Various  styles  of  screw 
threading  dies. 

When  it  is  necessary  to  cut  a  screw  to  size  or  to 
gauge,  it  is  generally  considered  advisable  to  make  the 
finish  die  of  a  form  known  as  an  adjustable  die.  The 
forms  referred  to  are  shown  above,  in  Fig.  66. 

The  solid  square  die,  being  used  mostly  for  thread- 
ing bolts  and  similar  work  where  accuracy  is  not 
essential,  are  usually  made  to  cut  small  enough,  and  no 
particular  pains  taken  when  they  are  hardened.     How- 

148 


Holder  for  hardening  screw  dies. 


ever,  if  a  die  of  this  form  is  hardened  all  over,  the  con- 
traction from  the  outside  edges  is  very  unequal,  on  ac- 
count of  the  corner  containing  more  stock  than  the 
portion  between.  Owing  to  the  unequal  contraction, 
the  cutting  edges  do  not  have  an  equal  amount  of 
work  to  do,  so  one  cutting  edge  dulls  more  rapidly 
than  the  other.  Every  tool  maker  knows  the  secret  of 
success  in  making  a  screw  threading  die  that  will  work 
satisfactory,  lays  in  having  each  cutting  edge  cut  its 
proportional  amount.  It  will  readily  be  seen  that  any 
unequal  contraction  or  wear,  which  causes  an  upsetting 
of  this  equality  in  cutting,  must  reduce  the  usefulness 
of  the  tool. 

Too  often  no  account  is  taken  of  the  amount  of  work 
a  tool  will  do  after  it  is  hardened.  If  it  survives  the 
ordeal  of  going  through  the  fire  and  water,  and  will 
cut,  it  is  considered  a  successful  job  of  hardening. 

From  the  preceding  it  will  be  seen  that  it  is  neces- 
sary, in  order  that  best  re- 
sults may  follow,  that  the 
die  be  in  (as  near  as  possi- 
ble) the  same  shape,  and 
the  location  of  the  cutting 
edges  be  the  same  as  be- 
fore hardening.  Now,  in 
order  to  accomplish  this 
result,  it  is  necessary  to 
treat  the  die  in  a  manner 
that  will  cause  the  cutting 
portion  to  harden  ^/-j/.  By 
so  doing,   the  contraction 

Figure  67.      Device  for  cooling  screw         ^^   the   OUtcr   portioU   doeS 
threading  dies.  UOt  SCrioUSly  aff  CCt  the  CUt" 


'^% 


How  to  prevent  "twist"  in  screw  dies. 

ting  qualities  of  the  tool.  When  hardening  a  square 
or  a  solid  round  die,  it  is  sometimes  considered  advis- 
able to  place  the  die  in  a  fixture,  as  shown  in  Fig. 
67.  It  is  then  immersed  in  the  bath  and  swung  slowly- 
back  and  forth  in 
order  that  the  liquid 
may  readily  pass 
through  the  opening, 
thus  insuring  the 
hardening  of  the  cut- 
ting teeth.  The  por- 
tion near  the  circum- 
ference is,  of  course, 
soft.  This  is  rather 
to  be  desired  than 
otherwise  in  the  form 
of  die  under  consid- 
eration. 

When  adjustable 
dies  are  hardened,  it 
is  generally  consid- 
ered necessary  to  harden  the  outer  portion  in  order 
to  furnish  a  certain  amount  of  elasticity,  in  order 
that  the  die  may  open 
uniformly  when  ex- 
panded. The  necessity 
of  this  depends  on  the 
design  of  the  die.  If 
stock  enough  is  left  at 
the  portion  where  the  die  is  supposed  to  spring,  the 
stiffness  of  the  stock  will  give  it  sufficient  tension. 
Should  it  be  necessary  to  harden  the  outer  portion 
somewhat,  the  fixture  may  be  cut  away  in  a  manner 


Figure  68.      Method  of  preventing  "twist' 
in  screw  threading  dies. 


Figure  69.      Example  of  "twist* 
in  screw  die. 


ISO 


Cooling  dies  for  screw  cutting. 

that  allows  the  contents  of  the  bath  to  come  in  contact 
with  the  steel  nearer  the  outer  edge. 

Adjustable  dies  of  the  description  shown  should  not 
be  cut  entirely  through  at  the  point  where  pressure  is 
applied  to  open  them,  but  may  be  cut  nearly  through, 


Figure  70.     Method  of  cooling  dies  for  thread  cuttmg. 

commencing  at  the  inside  and  cutting  toward  the  out- 
side, leaving  a  thin  partition,  as  shown  in  Fig.  68. 
This  partition  holds  the  die  in  shape,  preventing  the 
tendency  to  twist,  shown  in  Fig.  69. 

When  it  is  not  considered  advisable  to  make  or  use 
a  fixture  as  described,  the  die  may  be  grasped,  after 
being  heated,  with  a  pair  of  tongs,  as  shown  in  Fig. 
70,  and  quenched  in  a  bath  of  lukewarm  water  or 
brine,  swinging  it  slowly  back  and  forth,  as  repre- 
sented.    When  hardening  any  tool  of  this  description, 


Drawing  the  temper  of  a  "spring"  die. 

bear  in  mind  the  fact  that  the  article  should  never  be 
heated  in  a  manner  that  allows  the  cutting  teeth  to 
become  oxidized  by  exposure  to  the  air  while  heating. 
Best  results  are  obtained  by  heating  in  a  muffle  or  a 
piece  of  pipe.  If  the  surface  of  the  teeth  become 
covered  with  a  scale  of  oxide,  this  raises,  and  keeps  the 
contents  of  the  bath  from  acting,  thus  causing  soft 
spots,  which  render  the  tool  practically  useless. 

An  excellent  plan  consists  in  heating  the  dies  in  an 
iron  box  having  a  half  inch  of  charred  leather  in  the 
bottom.  Fill  the  opening  in  the  die  with  the  same 
material.  When  the  die  reaches  a  uniform  tempera- 
ture which  is  right  to  produce  the  desired  result, 
quench  in  the  bath. 

When  hardening  ** spring"  dies,  or,  as  they  are 
familiarly  termed  in  some  shops,  *' hollow  mill  dies," 
best  results  are  obtained  by  dipping  in  the  bath  with 
the  cutting  end  up- 


permost,  as  de- 
scribed under  Hard- 
ening Hollow  Mills. 


Figure  71. 
Drawing  the  temper  of 
'  'spring' 


Generally  speaking,  it  is  not  necessary  to  heat  the  die 
much  beyond  the  length  of  the  threads. 


152 


Tempering  small  dies. 

The  temper  may  be  drawn  by  placing  the  die  on  a 
hot  plate,  as  shown  in  Fig.  71,  drawing  from  the  back 
end.  On  account  of  the  shape  of  the  cutting  edge, 
which  makes  it  stronger  than  the  ordinary  form  of 
screw  threading  die,  it  is  not  necessary  to  draw  the 
temper  as  much.  A  faint  straw  color  making  them 
about  right,  unless  the  cutting  tooth  is  long  and  weak, 
in  which  case  it  may  be  drawn  to  a  full  straw  color. 

If  many  dies  are  to  be  tempered  at  a  time,  the  cost 
may  be  reduced  very  materially  by  heating  in  a  kettle 
of  oil,  drawing  them  to  a  temperature  which  varies 
from  460°  to  500°,  according  to  the  conditions  pre- 
viously mentioned. 

When  but  one  or  two  are  to  be  done,  it  is  advisable 
to  brighten  the  sides  and  draw  the  temper  by  laying 
them  on  a  flat  plate,  moving  around  on  the  plate,  and 
turning  them  over  occasionally.  The  temper  color 
should  be  from  a  straw  to  a  brown  color.  If  it  is  con- 
sidered advisable  to  draw  the  temper  of  a  large  batch 
of  dies  by  the  hot  plate  method,  the  plate  may  be 
placed  over  a  fire,  in  order  to  maintain  a  uniform  heat. 
Quite  a  number  of  dies  may  be  placed  on  the  plate  at 
a  time.  It  is  necessary  to  turn  them  occasionally,  as 
mentioned.  As  one  shows  the  proper  temper  color,  it 
may  be  removed  and  placed  in  a  dish  of  warm  oil.  By 
this  method  a  skillful  operator  can  temper  a  large  batch 
of  dies  in  a  comparatively  short  space  of  time,  but  the 
results  will  not  be  as  satisfactory  as  though  heated  in  oil. 

The  amount  of  work  to  be  done  will  always  deter- 
mine the  most  economical  method  of  doing  it,  but  it  is 
better  to  err  on  the  side  of  having  too  many  convenien- 
ces. A  few  spoiled  tools  will  pay  for  several  improve- 
ments. 

«53 


Cracking  of  dies  from  internal  strains. 

Larg-e  pieces  of  steel  are  more  liable  to  crack  as  a 
result  of  internal  strains  than  smaller  pieces.  On  ac- 
count of  the  weight  of  the  piece  there  is  a  tendency  on 
the  part  of  some  hardeners  to  neglect  reheating  the 
piece  to  overcome  this  tendency  to  crack,  due  to  various 
uneven  heats  the  steel  may  have  received. 

In  order  to  overcome  this  tendency,  the  die  should 
be  reheated  in  a  uniform  manner  to  a  temperature  that 
allows  the  various  portions  to  conform  to  any  strains 
in  the  piece.  This  may  be  accomplished  by  placing  the 
die  in  the  fire,  turning  it  occasionally,  in  order  that  it 
may  be  uniformly  heated,  and  heating  until  moisture 
applied  to  the  surface  forms  steam.  This  method  when 
applied  to  large  pieces  is  not  apt  to  result  in  the  center 
of  the  piece  being  heated  as  hot  as  the  outside.  Con- 
sequently better  results  will  follow  if  the  die  is  placed  in 
a  kettle  or  tank  of  boiling  water  (212°)  and  left  there 
until  heated  uniformly  throughout.  If  the  die  is  large 
this  will  necessitate  leaving-  it  in  the  water  at  the  boil- 
ing point  for  several  hours,  as  it  takes  longer  to  heat 
a  large  piece  of  steel  throughly  than  we  realize.  It 
pays  to  be  very  careful  about  these  little  points,  as  these 
dies  are  often  expensive. 

Hardening   Long  Articles. 

Most  hardeners  dread  hardening  long,  slender 
articles,  on  account  of  the  uncertainty  attending  the 
operation,  so  far  as  results  are  concerned.  If  the 
article  is  a  reamer  or  similar  tool,  having  teeth  on  the 
outer  surface,  it  will  not  require  as  great  an  amount  of 
heat  as  though  it  were  a  solid  piece.  In  any  case, 
however,  do  not  heat  any  hotter  than  is  necessary  to 

154 


Proper  way  to  harden  long  articles. 

accomplish  the  desired  result,  always  remembering 
that  even  heats  are  the  secret  of  success  when  heating 
steel  for  hardening.  If  the  tools  are  hotter  on  one  side 
than  the  other,  unequal  contraction  must  take  place ; 
consequently,  the  article  will  be  crooked. 

When  hardening  long  reamers  and  similar  tools,  it 

is   necessary    that    the 


Wrong 


Right 


heat  should  be  uniform 
and  as  low  as  possible. 
It  must  be  the  same 
on  each  side.  If  one 
side  be  a  low  red  and 
the  opposite  side  a 
bright  red,  and  it  is 
quenched  in  the  bath, 
it  is  sure  to  come  out 
crooked.  A  piece  of 
this  description  must 
be  dipped  in  the  bath 
in  as  nearly  a  vertical 
position  as  possible,  as 
shown  in  Fig.  72,  in 
order  to  cool  both 
sides  uniformly.  If 
it  be  dipped  at  very 
much  of  an  angle,  as 
shown  in  example  marked  *  'wrong, "  it  will  surely  spring, 
on  account  of  the  uneven  contraction  of  the  two  opposite 
sides.  It  is  necessary  to  work  such  pieces  up  and 
down  in  the  bath,  changing  the  location  occasionally  in 
order  to  avoid  the  effects  of  the  steam  generated. 

These  may  seem  like  unnecessary  precautions,  but 
the  results  obtained  will  show  that  it  is  worth  while 


Figure  72. 


The  Derry  CoUatd  Co. 


Proper  method  for  dipping 
long  articles. 


155 


Advantages  of  heated  baths. 

observing  them  as  thorouglily  as  possible.  It's  the 
little  things  that  count  in  successful  hardening  and 
tempering. 

Condition   of  the   Bath. 

If  the  tool  is  of  a  design  that  makes  springing  a 
possibility  when  the  article  is  quenched,  it  will  be 
necessary  to  warm  the  contents  of  the  bath  consider- 
ably, the  degree  to  which  it  should  be  heated  depend- 
ing on  the  shape  of  the  tool  and  the  temper  of  the  steel 
used.  Excellent  results  are  many  times  obtained  with 
a  bath  heated  to  a  temperature  of  ioo°  to  150°. 

The  writer  has  had  excellent  results  when  harden- 
ing articles  of  this  description  by  placing  them  in 
tubes  one  inch  larger  inside  than  the  piece  to  be 
hardened.  It  should  be  placed  in  the  center  of  the 
tube,  the  space  between  the  article  and  the  tube  being 
filled  with  charred  leather.  The  ends  should  be  stop- 
ped and  sealed  with  fire-clay.  The  tube  is  then  placed 
in  the  fire  and  given  a  uniform  heat  for  a  period  that 
insures  the  article  being  evenly  heated  to  the  desired 
temperature,  when  it  may  be  removed  from  the  tube 
and  plunged  in  a  warm  bath  of  brine  or  the  citric  acid 
solution. 


Hardening  Taps. 


It  is  necessary  to  take  into  consideration  the  design 
of  the  tool,  the  steel  used,  and  the  nature  of  the  work 
to  be  done  by  the  tap.  If  the  tool  is  very  long  and  it 
is  necessary  to  harden  but  a  small  portion  of  the  length, 
it  is  not  necessary  to  heat  it  any  farther  up  than  the 

156 


The  hardening  of  taps. 


length  wliicli  requires  hardening.     In  such  cases  it  is  a 
comparatively  simple  job. 

When  a  long  tap  requires  heating  and  hardening 
its  entire  length,  it  is  necessary  to  devise  some  way  of 

uniformly  heat- 


i-5^2Z%r:*L^^_ 


The  Derry  Collard  Co. 


ing  the  piece. 
It  is  also  neces- 
sary to  quench 
in  such  a  man- 
ner that  all  por- 
tions will  cool 
as  uniformly  as 
possible,  to 
avoid  unequal 
contraction, 
thus  preventing 
springing  or 
cracking. 

When  hard- 
ening taps,  care 
should  be  exer- 
cised that  the 
teeth  are  heated  no  hotter  than  the  refining  heat, 
or  they  will  be  brittle.  If  heated  hotter  than  nec- 
essary, it  must  have  the  temper  drawn  very  low,  or 
the  teeth  will  snap  off  when  used.  If  the  temper  is 
drawn  low,  as  described,  the  tap  is  too  soft  to  perform 
its  full  share  of  work.  When  hardening  tools  having 
teeth  or  projections,  it  is  essential  that  the  heat  be  the 
lowest  possible.  It  is  advisable  to  heat  in  a  muffle 
furnace  or  enclosed  in  some  receptacle  to  remove  it 
from  the  products  of  combustion  in  the  furnace  and 
from  oxidation  by  the   action  of  the  air.     When  it 


Supply  Pipe 

Figure  73. 


Bath  for  hardening  taps. 


157 


Bath  for  hardening  taps. 

reaches  a  low,  uniform  heat,  dip  in  the  bath  of  water 
or  brine,  preferably  the  latter.  Work  up  and  down 
rapidly,  to  bring"  the  contents  of  the  bath  in  contact 
with  the  teeth;  or,  better  still,  use  a  bath  as  shown 
in  Fig.  73,  having  inlet  pipes  on  opposite  sides  of  the 
tank,  these  pipes  being  perforated,  as  shown.  It  is 
advisable  to  have  the  piping  so  designed  that  the 
upright  perforated  pipes  may  be  placed  against  the 
side  of  the  tank  or  moved  toward  each  other,  in  order 
that  the  jets  coming  out  of  the  holes  may  strike  the 
object  with  sufficient  force  to  drive  the  steam  away, 
thus  allowing  the  liquid  to  act  on  the  steel. 

Long  taps  give  best  results  if  packed  in  a  tube 
with  carbon,  in  the  form  of  charred  leather,  as  de- 
scribed in  hardening  reamers.  When  it  has  reached 
the  proper  uniform  hardening  heat,  it  may  be  hardened 
by  immersing  in  the  form  of  bath  represented  in  Fig. 
73.  If  a  bath  of  this  description  is  not  at  hand,  very 
satisfactory  results  may  be  obtained  by  dipping  in  an 
ordinary  bath  of  the  desired  temperature,  and  revolve 
the  piece  rapidly  in  the  bath  to  insure  uniform  results. 
This  will  in  a  measure  imitate  the  bath  mentioned. 

A  bath  of  brine,  or  the  citric  acid  solution,  give 
excellent  satisfaction  for  hardening  tools  of  this  descrip- 
tion. Unless  the  tap  is  of  large  diameter,  do  not  use 
a  cold  bath. 

Hardening  Small   Taps,   Reamers, 
Counterbores,   Etc. 

When  small  articles  of  this  description  are  hardened 
in  great  quantities,  it  is  necessary  to  devise  means 

158 


Muffle  furnace  for  heating  taps. 

whereby  they  may  be  hardened  cheaply,  yet  the  work 
must  be  done  in  a  satisfactory  manner.  Various 
methods  are  employed  to  accomplish  this,  and  one  of 
the  most  successful  methods  that  has  come  to  the 
writer's  attention  consists  of  a  furnace  made  with  a 


r/////y//y///yy/^^^^^^^ 


Muffle 


b 


ml 


Fire  Box 


,J,^^,^/>,^,,,,^„,,^,,^y,^^,j-,^^/^/'^/\yy, 


Ash  Box 


Smoke 
Pipe 


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\ 

(? 

■NN 

^ 

J 

^ 

' 

°i-- 

=o 

<: 

OD^DD 

-V 

^~- 

V     1 

The  Derry  Collard  Co. 


Figure  74.     Muffle  furnace  for  heating  taps. 


muffle.  The  heat  was  furnished  by  burning  illuminat- 
ing gas,  or  it  may  be  designed  to  bum  coal.  The 
muffle  was  made  as  shown  in  Fig.  74.  Cleats  are  cast 
on  to  the  walls  of  the  muffle,  which  in  this  case  was 
cast  iron.  On  these  cleats  shelves  were  placed,  and 
on  these  shelves  the  pieces  to  be  hardened  were  heated. 
It  was  necessary  to  turn  the  pieces  over  occasionally  to 
insure  uniform  results. 

When  a  piece  was  heated  to  the  proper  tempera- 
ture, it  was  taken  by  means  of  a  pair  of  tongs  and 
dropped  into  a  bath,  which  consisted  of  a  tank  having 


159 


Bath  for  hardening  taps  and  reamers. 

several  tube-shaped  pieces  of  wire  netting,  as  shown  in 
Fig.  75.  The  tubes  were  slightly  larger  inside  than 
the  diameter  of  the  largest  part  of  the  tool  being 
hardened.  Tubes  of  various  sizes  were  used,  the 
size  depending  on  the  diameter  of  the  tools  to  be 
hardened.     The  tank  had  a  supply  pipe  coming  up 


fam\\\\\^^^^^^ 


Tlw-Detry  CoUard  Co. 

Figure  75.     Bath  for  hardening  taps  and  reamers. 


from  the  bottom.  This  was  connected  with  a  supply 
tank  overhead.  A  pump  was  used  to  force  the  water 
into  the  supply  tank.  It  was  possible  to  use  a  bath 
of  clear  water,  brine,  or  any  favorite  hardening 
solution.  In  this  case,  the  bath  consisted  of  the  citric 
acid  solution,  described  under  ** Hardening  Baths." 
It  was  kept  at  a  temperature  of  about  60°.  As  fast 
as  the  pieces  were  heated  to  the  desired  temperature, 
they  were  taken  with  tongs  and  dropped  into  one 
of  the  tubes,    the  cutting   end    being    down.     They 

160 


How  to  brighten  taps  to  show  color. 


passed  down  through  the  tubes  on  to  an  incline,  and 
then  into  a  catch  pan,  as  shown.  The  distance  the 
pieces  traveled  in  the  bath  was  considered  when 
designing  it.  It  was  found  by  experiment  that  the 
largest  piece  to  be  hardened  would  cool  below  a  red 
heat  in  falling  a  distance  of  two  feet  in  the  bath.  To 
make  satisfactory  results  a  certainty,  the  depth  of  the 

part  of  the  tank 
through  which  the 
pieces  passed  was 
made  36  inches.  If 
the  tools  had  struck 
the    bottom    and 


Figure  76. 

Grinding  to  show 

temper  color. 


turned  on  their  side  before  the  red  had  disappeared 
from  the  surface,  they  would  have,  in  all  probability, 
sprung ;  but,  as  it  was,  excellent  results  were  obtained. 
When  taps  are  brightened,  in  order  that  the  temper 
colors  may  be  visible,  it  is  not  advisable  to  use  a  piece 
of  emery  cloth  on  a  stick  or  round  file,  as  is  often  done, 
because  unless  the  operator  is  extremely  careful,  he  is 
apt  to  cut  away  the  cutting  edge  of  the  teeth,  thus 
rendering  the  tool  unfit  for  use.  If  possible,  use  an 
emery  wheel  of  the  shape  of  the  groove,  as  shown  in 
Fig.  76.  It  is  not  absolutely  necessary  to  use  a  fixture, 
as  the  tap  may  be  held  in  the  hands  for  brightening. 


161 


Other  ways  of  heating  taps. 

In  this  way,  not  only  is  the  steel  brightened,  so  the 
colors  may  be  readily  seen,  but  the  cutting  edges  are 
ground  sharp,  and  any  burrs  thrown  up  between  the 
teeth  are  ground  away. 

When  but  a  few  taps  are  to  be  tempered,  it  is  pos- 
sible to  heat  them  sufficiently  in  a  gas  jet  or  the  flame 
of  a  Bunsen  burner ;  sometimes  the  flame  of  a  candle 
is  used  when  the  article  is  very  small,  as  in  Fig.  77. 
With    a    blowpipe,    a   hot    flame    can    be    produced. 

When  the  taps  are  made  in  quantities  suffi- 
ciently large,  it  is  much  more  economical  to 
draw  the  temper  by  placing  in  a  kettle  of  oil, 
gauging  the  temperature  with  a  thermometer. 

The  amount  necessary  to  draw  the  temper 
of  a  tap  in  order  to  get  desired  results,  de- 
pends,   as    with   most 
other  cutting  tools,  on 
the  steel  used,  the  heat 
given  when  hardening, 
and  the  use  to  which  they  are  to 
be  put.     Very  small  taps  that  are 
to  be  used  by  hand  may  be  left 
harder   than    those   intended   for      The  oerry' couard  co. 
use   in   a   screw    machine.     Taps       Figure  77.    One  way  to 
used  by  hand   should   be   drawn  ^^^  ^"^^   ^^^^' 

to  deep  straw  or  brown  color,  while  those  used  on 
screw  machine  work  need  drawing  to  a  deep  brown, 
and  in  some  cases  to  a  purple. 

Half  Round   Reamers. 

These  should  be  heated  very  carefully  in  a  pipe  or 
muffle  furnace  to  the  lowest  heat  possible  to  harden. 

162 


Method  for  cooling  half-round  reamers. 


When  dipping  in  the  bath,  the  reamer  should  be  in- 
clined somewhat  from  a  perpendicular  position,  the 
heavier  portion  being  on  the  lower  side,  as  shown  in 
Fig.  78,  to  avoid  a  tendency  to  spring.  The  contents 
of  the  bath  should  be  heated  as  warm  as  is  consistent 
with  good  results,  as  this  will  help  keep  it  straight. 

Should  the  ream- 
er spring  somewhat 
in  hardening,  it 
may  be  straight- 
ened by  reheating 
and  exerting  a 
pressure  on  the 
convex  side. 

If  the  projection 
has  been  left  on  the 
end,  as  shown  in 
Fig.  79,  the  reamer 
may  be  placed  be- 
tween centers  and 
straightened,  as 
represented  else- 
where. 
Should  it  be  a  reamer  having  no  center  at  the 
small  end,  it  may  be  placed  on  two  V  blocks,  as  shown 
in  Fig.  80.  Apply  heat  by  means  of  a  gas  jet,  spirit 
lamp,  or  any  other  means  to  the  lower  side,  heat  until 
oil  placed  on  the  surface  commences  to  smoke.  Now 
apply  pressure  at  P,  on  top  side.  When  it  has  been 
sprung  the  proper  amount,  cool  by  means  of  wet 
waste. 

The  possibility  of  straightening  reamers  and  sim- 
ilar work  means  such  a  saving  in  many  shops  that  it 

163 


Figure  78.     Proper  method  for  cooling 
half-round  reamers. 


Hardening  milling  cutters. 

will  pay  to  have  special  attention  paid  to  it,  as  crooked 
tools  of  any  kind  cannot  do  accurate  work.  It  will 
pay  to  rig  up  fixtures  especially  for  this,  as  the  saving 
is  far  greater  than  the  cost. 

Small,  half-round  reamers  should  be  drawn  to  a 
full  straw,  or  a  brown  color  for  most  work. 


Hardening  Milling  Machine  Cutters. 

As  most  shops  have  at  least  one  milling  machine, 
and  many  shops  hundreds,  there  are  probably  more 
cutters  hardened  for  this  class  of  work  than  for  any 
other. 

In  hardening  this  class  of  tools,  it  is  necessary  to 


The  Derry  CoUard  Co. 


id 


Figure  79.     Half-round  reamer. 


have  them  hard  enough  to  cut  the  metal  being 
machined,  yet  tough  enough  to  stand  up  under  the 
strain  to  which  it  must  be  subjected. 

Milling  machine  cutters  should  be  hardened  at  a 
lower  heat  than  a  solid  piece  of  the  same  size.  The 
teeth,  being  slender  and  projecting  from  the  solid 
body,  take  heat  very  readily.  When  possible,  tools  of 
this  description  should  be  annealed  after  a  hole  some- 
what smaller  than  the  finished  size  has  been  drilled 
and  the  tool  blocked  out  to  shape  in  order  to  overcome 
the  tendency  to  crack  from  internal  strains.  If  it  has 
not  been  possible  to  do  this,  or  if  for  any  reason  it  has 

164. 


Care  in  heating  milling  cutters. 

not  been  considered  advisable,  the  cutter  may  be  heated 
to  a  low  red  and  laid  to  one  side  and  allowed  to  cool 
until  the  red  has  disappeared,  when  it  may  be  reheated 
and  quenched.  It  is  always  better,  however,  to  anneal 
after  blocking  out  if  it  can  be  planned  so  as  to  take 
the  time  necessary  to  do  this.  The  results  are  more 
satisfactory  in  every  way. 

It  may  be  well  to  again  caution  the  reader  in  regard 
to  the  heats.  The  teeth  of  this  form  of  tool  being  thin, 
are  apt  to  absorb  heat  faster  than  one  realizes,  and  as 
a  consequence,  they  become  too  hot.     If  a  cutter  is 


The  Derry  Collard  Co. 

Figure  80.     Straightening  a  half-round  reamer. 


overheated,  it  will  not  do  as  much  nor  as  satisfactory 
work  as  though  properly  heated ;  but  should  the  teeth 
by  any  carelessness  become  overheated,  do  not  quench 
at  that  heat,  thinking  no  one  will  know  the  difference. 
While  it  is  possible  to  misrepresent  the  condition  of 
the  heat  when  describing  it,  the  texture  of  the  steel 
always  tells  the  truth  in  regard  to  what  the  operator 
has  done  with  it  when  in  the  fire.  Neither  is  it  a  good 
plan  to  hold  it  in  the  air  and  let  it  cool  until  the  color 
shows  about  right,  because  it  is  hotter  inside  than  on 
the  outside ;  and  then  again,  the  grain  will  be  as  coarse 

165 


How  to  cool  milling  cutters. 


as  thougli  it  were  dipped  at  the  higher  heat.  It  should 
be  allowed  to  cool  off  and  then  heated  to  the  refining 
heat  and  quenched. 

When  this  form  of  tool  is  ready  to  harden,  place  it 
on  a  wire,  bent  as  shown  in  Fig.  8i.  The  wire  should 
be  large  ^  enough  to  hold  the  cutter  without 
bending,  ^,^  but  not  much  larger,  as  it  should 
not  impede  ^^  the  circulation  of  the  fluid  through 
the  hole  of  the  ^^  cutter.  Neither  should  any  con- 
siderable sized  ^^  piece  of  steel  rest  against  the 
side  of  the  cutter,  ^^  as  the  action  of  the  bath 
would  not  be  uni-  ^^  form  if  it  were  kept  away 
from  some  portions  ^^  of  the  piece.  The  cutter 
should  be  worked  ^^^  around  well  in  the  bath 
until  the  teeth  are  hard,  ^^^  when  it  may  be  re- 
moved and  plunged  in  oil  ^^^  and  left  until  cold. 
It  should  then  be  taken  and  ^^  held  over  a  fire 
and  heated  sufficiently  to  re-  ^.  move  any  ten- 
dency to  crack  from  internal  ^  strains.  The 
temper  may  now  be  drawn  the  re-  quired  amount. 

A  method  in  use 
in  many  shops,  con- 
sists in  dipping  the 
cutter  in  a  bath  of 
water  having  one  or 
two  inches  of  oil  on 
the  surface.  The 
cutter  is  passed  down  through  the  oil  into  the  water. 
Fig.  82  shows  a  bath  of  this  description.  The  oil  does 
away  with  the  first  sudden  shock,  which  results  when 
hot  steel  is  plunged  into  cold  water,  and  as  a  small 
portion  of  the  oil  adheres  to  the  teeth,  especially  in  the 
comers  where  the  teeth  join  the  body  of  the  material, 

166 


liM-Drnj  CoUard  Co. 


Figure  81.     Proper  way  to  cool 
milling  cutters. 


Drawing  temper  of  milling  cutters. 

the  action  of  the  water  is  not  as  **rank"  as  would 
otherwise  be  the  case.  Where  the  teeth  are  long  or 
the  mill  is  of  irregular  contour,  it  is  advisable  to  heat 
the  water  somewhat.  Water  or  brine,  heated  luke- 
warm, works  fully  as  well  as  though  cold  on  tools  of 
this  description  and  is  not  as  likely  to  crack  them. 
When  the  outline  is  very  irregular  and  the  tool  is  made 
of  high  carbon  steel,  the  writer  has  had  excellent  suc- 
cess using  a  bath  of  brine  heated  to  80°  Fahr.  The 
idea  that  a  bath  must  be  as  cold  as  possible  has  prob- 
ably ruined  more  steel  than  we  realize. 

Drawing  Temper  of  Milling  Machine 
Cutters. 


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I  II   I  II    I  I  II       I 

■'i|l  |i||i|0  |li|l""'  ' 
III  I  !i    i:i.!!i! 


III   :| 


niTg 


r^ri^-zznWatec: 


A  method  in  very  general  use  for  drawing  temper 
of  milling  machine  cutters,  consists  in  placing  the 
hardened  cutter  on  an 
iron  plug  of  the  form 
shown  in  Fig.  83,  the 
plug  having  been  pre- 
viously heated  suffici- 
ently to  draw  the  tem- 
per of  the  cutter. 

The  plug,  when 
heated,  should  not  fill 
the  hole  in  the  cutter. 
In  order  to  heat  the 
cutter  uniformly,  it 
should  be  turned  con- 
stantly on  the  plug. 

It  is,  of  course,  necessary  to  brighten  the  backs 
167 


7////////////////////////////////^////////////^^^ 


TTut  T>errv  Collard  Co. 

Figure  82.     Oil  and  water  bath  for 
milling  cutters. 


Heating  milling  cutters  on  a  plug. 

of  the  cutter  teeth  in  order  that  the  temper  colors 
may  be   readily   discerned. 

The  writer  has  had  best  results  by  holding  the 
cutter  over  a  fire,  or  a  hot  plate,  and  warming  the 
circumference  to  a  degree  that  made  it  impossible  to 


Figure  S3.      Plug  for  heating  milling  cutters. 


hold  the  hand  on  it,  previous  to  placing  the  cutter  on 
the  plug.  It  was  then  placed  on  the  plug  and  turned 
constantly  until  the  proper  temper  colors  showed, 
when  it  was  plimged  in  oil  to  prevent  its  getting  too 
soft. 

The  object  attained  in  heating  the  outer  surface 
first,  was  that  the  heat  given  was  sufficient  to  make 
the  steel  at  this  point  somewhat  pliable;  whereas,  if 
the  cutter  had  been  placed  when  cold  on  the  red  hot 
plug,  the  cutter  absorbing  the  heat  would  tend  to 
expand  the  steel  toward  the  outer,  rigid  surface.  If 
this  expansion  should  prove,  as  it  does  many  times,  to 
be  greater  than  the  steel  could  stand,  cracks  would 
result. 

The  amount  of  heat  necessary  to  give  a  milling 
machine  cutter  when  drawing  temper  can  not  be  stated 
arbitrarily.     It  is  desirable  to  leave  it  as  hard  as  possi- 

168 


Hardening  shank  mills. 

ble,  and  yet  not  have  it  too  brittle  to  stand  up  when 
in  use ;  consequently,  it  should  not  be  heated  any  hot- 
ter than  necessary  when  hardening.  It  should  not  be 
plunged  in  a  bath  of  extremely  cold  fluid,  neither 
should  it  be  checked  in  cold  water  when  the  temper 
has  been  drawn  sufficiently. 

While  it  is  not  considered  advisable  by  many 
mechanics  to  make  cutters  of  this  description  of  a  high 
carbon  steel,  the  writer's  experience  has  convinced 
him  that  better  results  are  obtained  by  using  a  high 
carbon  steel  extremely  low  in  phosphorus,  and  using 
extreme  care  in  the  heating.  Then  quenching  in  a  bath 
of  warm  brine,  80°  to  100°  Fahr. 

For  ordinary  work,  a  faint  straw  color  (430**)  gives 
best  results,  although  it  may  be  necessary  at  times  to 
draw  to  a  full  straw  color,  460°. 

A  kettle  of  oil,  heated  to  the  desired  temperature, 
furnishes  an  ideal  method  of  tempering  cutters  of  this 
description.  This  method  has  been  ftdly  described 
under  the  proper  section  on  pages  121  and  122,  and 
should  be  carefully  considered  in  connection  with  tools 
of  this  character 

Hardening  Shank   Mills, 

The  percentage  of  carbon  necessary  to  give  the 
best  results,  depends  on  the  make  of  steel.  For  ordin- 
ary work,  however,  a  steel  having  i  %  per  cent,  gives 
good  results. 

The  methods  employed  in  heating  and  quenching 
shank  mills  when  hardening,  depend  in  a  measure  on 
the  form  of  the  mill  and  the  custom  in  the  individual 
shop.     Mills  of  the  form  shown  in  Fig.  84,  may  be 

169 


Best  way  to  harden  shank  mills. 

heated  to  a  uniform  low  red  heat  for  a  short  distance 
above  the  teeth,  stopping  the  heat  in  the  necked  portion, 
marked  a.  In  some  shops  it  is  the  custom  to  leave 
the  shank  quite  a  little  larger  than  finish  size  in  order 
that  it  may  be  turned  to  size  in  the  lathe  and  fitted  to 


Figure  84.      How  to  harden  shank  mills 

the  collet  or  spindle  after  hardening.  In  such  cases  it 
is  necessary  to  leave  the  shank  soft  its  entire  length. 
In  other  shops  it  is  the  custom  to  turn  the  shank  nearly 
to  size  before  hardening,  leaving  on  just  enough  to 
allow  for  grinding  to  a  fit  and  remove  any  untruth 
resulting  from  springing  in  hardening.  If  it  is  neces- 
sary to  leave  the  shank  soft  its  entire  length,  care 
should  be  exercised  in  heating  and  dipping  in  the  bath 
that  the  shank  is  not  hardened  in  the  least.  If  it  is  to 
be  ground  to  a  fit,  the  same  care  is  not  necessary, 
although  greater  care  must  be  exercised  in  grinding  if 
the  shank  is  hard  for  a  short  distance  and  the  balance 
is  soft ;  but  if  careful  when  taking  the  finishing  cuts  on 
the  grinder,  no  trouble  need  be  experienced.  If  the 
cutter  is  made  as  represented  in  Fig.  85,  it  will  be 
necessary,  in  order  to  harden  the  teeth  the  entire  length 
in  a  satisfactory  manner,  to  harden  the  shank  for  a 
short  distance. 

When  hardening  a  cutter  of  the  description  shown 

170 


Treatment  of  holes  in  shank  mills. 

in  Fig.  86,  having  a  recess  of  considerable  depth  in  the 
end,  much  better  results  will  be  obtained  if  it  is  dipped 
in  the  bath  with  the  hole  uppermost,  as  shown  in  Fig. 
87 — that  is,  provided  it  is  necessary  to  harden  the  walls 
of  the  hole.  If  this  were  not  desirable,  then  it  would 
be  safest  to  fill  the  hole  with  fire-clay,  mixed  with 
water,  to  the  consistency  of  dough,  and  the  cutter 
dipped  as  shown  on  next  page.  If  the  hole  was  not 
filled  and  the  cutter  was  dipped  in  the  bath  with  the 
hole  down,  the  steam  generated  would  drive  the  water 
away  from  the  teeth  at  end;  and  furthermore,  the 
steam  would  very  likely  cause  the  thin  walls  to  crack. 


TtM  Shrry  C«lUrd  Co. 


Figure  85. 


Figure  86.     Shank  mills. 


When  hardening  cutters  of  the  form  shown  in  Fig. 
88,  known  as  T  slot  cutters,  it  is  necessary  to  harden 
the  entire  length  of  portion  necked  below  size  of 
shank  for  several  reasons.  When  the  neck  portion  is 
slender,  this  is  necessary,  in  order  to  strengthen  this 

171 


Treatment  of  T  slot  cutters. 

portion  so  it  will  not  spring  or  twist  off  when  the  cutter 
is  in  operation.  If  the  cutter  is  of  a  size  that  makes 
the  necked  portion  large  and  strong  enough  to  resist 
the  cutting  strain,  it  might  not  appear  at  first  thought 
necessary  to  harden  this.  But  as  it  ^  is  g  e  n  e  r 
ally  made  but  a  few  thousandths  of  an    inch 

smaller  than  the  slot  it  travels  in,  it  will,  if  left 

soft,  become  roughed  up  by  the  fine  cast    iron 

chips,  which  are  liable  to  get  between  the  walls 

of  the  slot  and 
the  stem.  Con- 
sequently, it  will 
be  readily  seen 
that  in  most  cases 
it  is  advisable  to 
harden  the  entire 
length  of  the 
necked  portion. 

If  there  is 
considerable  dif- 
erence  between 
the  size  of  the 
cutting  portion 
and  the  shank 
of  the  tool,  the 
cutter  should  be 
made,  if  possible, 
with  a  fillet  in  the 
comer,  as  shown  at  a^  in  sectional  view  of  Fig.  89.  If, 
however,  this  precaution  has  not  been  taken,  or  it  has 
not  been  possible  to  do  it,  a  piece  of  iron  wire  may  be 
wound  around,  as  shown  at  5.  This  wire  being  red- 
hot  when  the  cutter  is  dipped  in  the  bath,  has  the  effect 


Figure  87.      Proper  method  for 
treating  shank  mills. 


172 


Tlie  Derry  Collard  Co. 

Figure  88.     T  slot  cutter. 


Fillets  for  T  slot  cutters. 

of  keeping  the  contents  of  the  bath  away  from  the 
sharp  comer  until  the  larger  and  smaller  portions  of 
the  mill  have  become  hardened  to  a  degree,  thus  reduc- 
ing the  liabil- 
ity of  cracking 
at  this  point. 
When  the  cut- 
ter has  been 
heated  to  a  low 
red,  it  should 
be  plunged  into  a  bath  of  water  or  brine  from  which 
the  chill  has  been  removed ;  work  around  well  in  the 
bath  until  it  is  of  the  same  temperature  as  the  bath, 
when  it  may  be  removed  and  the  temper  drawn. 

If  it  has  not  been  possible  to  heat  the  cutter  in  a 
muffle  or  in  a  piece  of  pipe  or  other  receptacle,  it  will 
be  found  an  excellent  plan  to  have  a  strong  solution  of 
potash  and  water,  which  should  be  heated  quite  warm. 
Before  the  cutter  is  heated, 
it  may  be  plunged  into  the 
potash  solution.  Place  it 
in  the  fire  and  heat  to  the 
proper  hardening  temper- 
ature and  plunge  in  the 
hardening  bath.  The 
effect  of  the  potash  is  to 
cause  any  thin  scale  of  oxide  which  may  have  formed  on 
the  surface  to  drop  off  the  instant  the  tool  touches  the 
bath.  If  this  scale  adheres  to  the  piece,  it  has  a  tend- 
ency to  rise  in  the  form  of  a  blister  when  in  contact 
with  a  cool  liquid,  and  consequently  it  keeps  the  con- 
tents of  the  bath  from  acting  on  the  steel  directly 
underneath. 


Figure  89.     Fillets  for 
T  slot  cutters. 


173 


Drawing  temper  of  T  slot  cutters. 

When  drawing  the  temper  of  a  tool  of  this  descrip- 
tion it  is  necessary,  in  order  that  the  necked  portion  be 
as  strong  as  possible  (especially  if  it  is  slender),  to 
draw  it  to  a  purple  or  even  a  blue  color,  while  the  cut- 
ting teeth  need  drawing  to  a  straw  color. 

It  is  surprising  to  one  not  thoroughly  posted  in  the 
effects  of  different  degrees  of  heat  on  steel  to  find  how 
hard  a  cutter  of  this  kind  may  be  left  if  it  was  properly 
heated  when  hardened.  This  is  best  seen  by  compar- 
ing with  one  that  was  heated  a  trifle  too  hot,  yet  not  to 
a  degree  that  is  generally  considered  harmful  to  the 
steel.  In  the  case  of  the  cutter  properly  heated — that 
is,  to  the  refining  heat — it  may  be  left  when  tempering 
at  a  faint  straw  color,  while  if  given  a  trifle  more  heat, 
it  is  necessary  to  draw  it  to  a  full  straw,  a  difference 
of  30°  of  heat,  and  a  vast  difference  in  the  amount  of 
work  it  will  do  between  grindings.  In  order  to  suc- 
cessfully draw  the  temper,  the  necked  portion  may  be 
placed  in  the  flame  of  a  gas  jet,  a  Bunsen  burner,  the 
flame  of  a  spirit  lamp ;  or,  if  none  of  these  are  avail- 
able, and  it  is  necessary  to  use  a  blacksmith's  forge  for 
all  work  of  this  description,  a  piece  of  sheet  iron  having 
a  hole  in  it  may  be  placed  over  the  fire.  A  jet  of  flame 
will  come  through  the  hole,  which  may  be  made  to 
strike  the  necked  portion.  In  this  way  the  desired 
temper  may  be  obtained. 

Hollow   Mills. 

When  articles  having  a  hole  running  part  way 
through  them,  as,  for  instance,  the  hollow  mill  shown 
in  Fig.  90,  are  to  be  hardened,  it  is  advisable  to  dip 

174 


Hardening  hollow  mills. 

them  in  the  bath,  with  the  opening  uppermost,  as  re- 
presented in  Fig.  91.  If  the  mill  were  dipped  with  the 
opening  down,  it  would  be  almost  impossible  to  get 
water  to  enter  the  hole  for  any  considerable  distance, 


Figure  90.     A  hollow  mill. 

as  the  steam  generated  would  blow  the  water  out.  As 
a  consequence,  the  walls  of  the  hole  would  not  harden, 
and  the  steam  would  in  all  probability  cause  the  steel 
to  crack. 

Then  again,  best  results  will  follow  if  the  frail  end 
is  not  chilled  until  after  the  heavier,  solid  portions  have 
contracted  somewhat.  If  the  lighter  portions  are  chil- 
led and  contracted  before  the  heavier  ones,  the  tend- 
ency is  for  the  heavier  parts,  which  are  stronger  than 
the  lighter,  to  pull  them  into  conformity  with  them- 
selves, and  as  the  steel  is  hard  and  rigid,  it  must  crack. 
While  this  principle  is  explained  elsewhere  in  this 
work,  it  seems  wise  to  show  the  adaptability  of  this 
peculiarity  of  steel  to  pieces  of  this  description. 

When  making  articles  having  holes,  as  shown,  if 
the  piece  is  to  be  hardened,  the  liability  of  cracking 
will  be  lessened  if  the  stock  at  the  end  of  hole  is  left, 
as  shown  in  Fig.  92.     If,  however,  the  piece  is  made 


»7S 


Tepid  water  for  hardening  hollow  mills. 


with  a  sharp  comer,  as  shown  in  Fig.  93,  it  is  advisable 
to  fill  in  this  sharp  comer  with  fire  clay,  or  graphite, 
in  order  that  there  may  be  no  pronounced  difference  in 
the  contraction  of  the  two  portions. 

When  hard- 
ening pieces  of 
this  character,  it 
is,  generally 
speaking,  good 
practice  to  use  a 
bath  of  tepid 
water  or  brine. 

When  it  is  con- 
sidered desirable 
to  harden  a  piece 
a  certain  dis- 
tance, and  no  far- 
ther, and  the  fa- 
cilities for  heat- 
ing do  not  allow 
of  heating  ex- 
actly the  right 
distance,  it  is 
necessary  to  dip 
in  the  bath  with 
the  teeth  down. 
In  order  to  over- 
come the  tendency  of  the  steam  to  blow  the  water 
from  the  hole,  a  small  vent  hole  is  drilled  through  the 
wall  of  the  piece,  as  shown  in  Fig.  94.  If  this  hole  is 
large  enough  to  allow  the  steam  to  escape,  good  re- 
sults will  follow  if  a  bath  is  used  having  a  jet  of  water 
coming  up  from  the  bottom,  as,  by  this  means,  water  is 

176 


The  Derry  Collard  Co» 

Figure  91.     Method  for  hardening 
hollow  mills. 


Various  types  of  hollow  mills, 

forced  into  the  hole.     However,  the  operator  should 
bear  in  mind  that  it  is  never  good  practice  to  have 


Figure  92. 
Hollow  mill  with 
rounded  corners. 


The  Derry  CoUard  Co. 

the  hardening  stop  at  a  shoulder,  either  inside  or  out- 
side of  a  piece  of  steel.     Where  possible,   stop   the 


Figure  93. 

Hollow  mill  with 

sharp  corners. 


hardening   somewhat   short   of    the  shoulder,    but  if 
this  does  not  meet  the  requirements,  harden  a  trifle 


Figure  94. 

Hollow  mill  with  hole 

to  allow  escape 

of  steam. 


beyond  the  shoulder.  This  may  seem  like  a  little 
thing  to  bother  about,  but  it  generally  means  the  dif- 
ference between  a  good  job  and  a  poor  one,  and  it's 


177 


Hardening  thin  articles. 

one  of  the  little  points  that  count  in  making  a  success- 
ful hardener. 

Thin  Articles. 

Thin  articles,  as  screw  slotting  saws,  metal  slitting 
saws,  etc.,  may  be  hardened  between  two  plates  whose 
faces  are  covered  or  rubbed  with  oil.  If  reasonable 
care  is  exercised  in  the  operation,  they  will  be  very 
straight. 

It  is  essential,  in  order  to  get  good  results,  to  heat 
the  pieces  on  a  flat  plate.  They  should  be  heated  no 
hotter  than  is  necessary  to  accomplish  the  desired  result. 
When  at  the  proper  heat,  the  saw  may  be  taken  by  a 
pair  of  tongs,  of  the  form  shown  in  Fig.  95,  and  placed 
on  a  plate  whose  face  is  covered  with  lard,  sperm 
or  raw  linseed  oil.  The  advantage  derived  from  using 
tongs  of  this  description  is,  the  saw  is  held  by  the  por- 
tion near  the  hole,  rather  than  by  the  teeth,  as  would 
be  the  case  if  a  pair  of  the  ordinary  style  were  used. 
In  that  case,  the  teeth  grasped  by  the  tongs  would  not 
be  of  the  same  temperature  as  the  balance  of  the  saw ; 
and,  as  a  consequence,  the  hardening  would  not  be 
uniform.  Another  plate,  whose  face  has  been  treated 
in  a  similar  manner,  may  be  placed  on  top  of  the  saw 
and  held  there  until  the  saw  is  cold.     It  is  necessary  to 


Figure  95. 
The  Derry  Coiiard  Co.      Tongs  for  holding  flat  plates. 

place  the  top  plate  in  position  as  quickly  as  possible, 
after  the  saw  has  been  placed  on  the  lower  plate. 

If  the  saw  should  become  chilled  before  the  upper 

178 


Method  of  cooling  flat  plates. 

plate  is  placed  on  it,  it  will  spring  somewhat,  and  the 
upper  plate  cannot  straighten  it.     Should  it  be  sprung 


II  II  II  II 


II  II  II II II 


y/////f//^^/^/^////j//Mf/^//wj,j//:r//f/. 


Figure  96.      Device  for  cooling 
thin,  flat  work 


'The  Derry  Coltard  Co. 


very  much,  the  pressure  applied  to  the  upper  plate 
will,  in  all  probability,  break  the  saw,  as  it  would  be 
hard  and  unyielding. 

If  many  pieces  of  the  description  mentioned  are  to 
be  hardened,  it  is  advisable,  for  the  sake  of  economy,  to 
make  a  special  device  for  chilling  the  work,  as  when 
two  plates  are  used,  it  is  necessary  to  have  the  services 
of  tvv^o  men,  one  to  handle  the  saws,  and  one  to  work 
the  movable  plate.  If  the  number  of  pieces  to  be 
hardened  does  not  warrant  an  expensive  apparatus, 
two  flat  plates  may  be  used,  drilling  two  holes  in  each 
plate,  as  shown  in  Fig.  96.  The  holes  in  the  lower 
plate  should  be  a  driving  size  for  ^  inch  wire,  while 
those  in  the  upper  plate  should  be  -^  inch  larger  than 


179 


Devices  for  hardening  thin  plates. 

the  size  of  the  wires.  A  cord  should  be  attached  to 
the  upper  plate,  as  shown.  This  cord  should  pass 
over  a  pulley  and  return  to  a  treadle.     The  operator, 


a 


u 


Qel 


r:  r.z:  i       x*> 


'.-.: 


O Q: 


lerffjri  <D\ 


0=0=; 


de  Dsrry  Collani  Co. 

Figure  97.     Device  for  hardening  between  plates. 

by  using  this  device,  can  handle  the  saws  and  operate 
the  plate  very  nicely. 

In  Fig.   97  a  device  is  shown  for  hardening  thin 
pieces  between  plates,  which  consists  of  the  base  a, 

I  go 


Necessity  for  keeping  jaws  of  plate  holders  cool. 

and  slide  ^,  to  which  are  attached  jaws  cc.  Through 
the  jaws  are  several  wires  for  the  work  to  rest  on  when 
it  is  placed  between  the  jaws.  The  side  is  operated  by 
the  treadle  <?,  which  is  connected  to  the  base  and  slide 
by  the  brackets  ff.  The  device  is  supported  by  the 
legs  as  shown.  The  advantage  derived  from  using  a 
fixture  having  the  jaws  standing  in  a  vertical  line,  as 
shown,  is,  the  piece  of  work  is  not  as  liable  to  chill  while 
closing  the  jaws,  as  would  be  the  case  were  the  jaws 
in  a  horizontal  position. 

If  the  work  is  hardened  in  large  quantities  and  the 
jaws  show  a  tendency  to  get  hot,  they  may  be  cast  hol- 
low and  a  water  pipe  connected  with  each,  providing 
an  outlet  on  the  opposite  side.  In  this  way  a  circula- 
tion of  water  may  be  kept  up  through  the  jaws,  thus 
keeping  them  cool  at  all  times.     In  order  to  insure  a 


The  Derry  Collard  Co. 

Figure  98.     Cooling  plate  mounted  on  springs. 


uniform  circulation  of  the  water,  it  will  be  necessary 
to  have  the  inlet  pipe  at  the  lower  edge,  on  one  end  of 
the  jaw,  and  the  outlet  pipe  on  the  upper  edge  at  oppo- 
site end.  The  outlet  pipe  should  be  carried  far  enough 
to  do  away  with  any  liability  of  any  of  the  water  get- 
ting on  the  surfaces  of  the  jaws  that  were  to  come  in 
contact  with  the  pieces  being  hardened. 

J8i 


Cooling  gun  springs. 

When  saws  or  other  pieces  of  considerable  thickness 
are  hardened  between  plates,  it  is  sometimes  necessary 
to  provide  for  a  supply  of  oil  around  the  teeth  when 
the  plates  are  in  position.  In  order  to  do  this,  it  is 
necessary  to  use 
plates  in  a  horizontal 
position,  as  shown  in 
Fig.  98,  having  the 
lower  plate  resting  on 

^  °  Figure  99.     Gun  spring. 

Springs,  or  other  ar- 
rangement to  keep  its  upper  face  above  the  surface  of 
the  oil  in  the  pan,  until  the  work  has  been  placed  on 
it.     The  pressure  applied  by  the  upper  plate  must 


Th«  Derry  CoUard  Co. 

Figure  100.      Method  for  cooling  gun  spring  shown  above 
or  other  irregular  pieces. 

submerge   them   in  the   oil   in   pan   to   a   depth   that 
insures  the  teeth  being  well  covered  with  oil. 


Drawing  temper  of  slitting  saws. 

When  drawing  the  temper  of  tools  of  this  descrip- 
tion best  results  can  be  obtained  by  putting  the  pieces 
in  a  kettle  of  oil,  gauging  the  heat  by  a  thermometer. 
While  the  degree  of  heat  necessary  to  produce  the 
desired  result  can  not  be  given  arbitrarily,  as  very 
much  depends  on  the  steel  used,  the  amount  of  heat 
given  when  hardening,  and  the  use  to  which  it  is  to  be 
put.  But  ordinarily,  metal  slitting  saws  for  general 
jobbing  purposes  should  be  drawn  to  460  degrees. 
Screw  slotting  saws,  -^  inch  thick  and  under,  525  de- 
grees.    If  thicker,  do  not  draw  as  low. 

The  method  of  hardening  between  plates  may  be 
applied  to  pieces  having  other  than  flat  forms.  Take, 
for  instance,  springs  which,  in  order  to  maintain  a 
given  tension,  must  be  of  a  certain  shape ;  for  example, 
the  main  spring  of  a  gun,  as  represented  in  Fig.  99. 
The  form  of  spring  is  shown  at  a,  while  dd  is  a  pair  of 
plates,  having  their  faces  formed  to  harden  the  spring 
and  keep  it  in  the  proper  shape.  It  is  not  generally 
desirable  or  advisable  to  use  a  form  when  hardening 
springs  of  this  character,  but  is  sometimes  necessary. 
The  method  and  amount  necessary  to  draw  the  temper 
of  springs  is  given  under  Spring  Tempering,  and  to 
avoid  repetition  the  reader  is  referred  to  that  section. 
It  has  seemed  necessary  to  repeat  some  statements  in 
order  to  show  their  different  applications  and  to  im- 
press them  on  the  mind. 

Screw-Drivers. 

There  is  probably  no  one  article  so  generally  used 
as  the  screw-driver  that  gives  so  much  trouble.  In  the 
first  place,  not  more  than  one  man  in  ten  understands 
how  to  properly  make  the  tool,  and  then  but  a  small 

183 


How  to  make  a  proper  screw-driver. 


percentage  of  this  one-tenth  can  harden  and  temper  it 
properly  after  it  is  made. 

A  screw-driver  is  better  for  having  been  forged  to 
shape,  provided  it  is  forged  properly ;  that  is,  heated 
properly  and  hammered  in  a  scientific  manner.  Unless 
one  understands  these  operations  well  enough  to  do  a 
good  job,  it  is  advisable  to  file  or  machine  one  from 
the  bar. 

A  screw-driver  should  be  made  with  the  end  that 
enters    the    screw 


ir 

a 


V 


Figure 


Tlie  Derry  CoUard  Co. 

Styles  of  screw-driver  points. 


slot  of  an  equal 
thickness  through- 
out, and  to  nearly 
fill  the  slot.  At 
times,  this  precau- 
tion is  observed, 
and  the  portion 
immediately  ad- 
joining is  made 
much  heavier  and 

with  square  comers,  as  shown  at  a,  Fig.  loi.  Now,  on 
account  of  the  unequality  of  size  of  the  adjoining  por- 
tions, it  is  a  difficult  matter  to  harden  and  temper 
it  uniformly  throughout.  Then  again,  the  shape  is 
such  that  it  must  break  where  the  heavy  and  light  por- 
tions adjoin,  on  account  of  the  unequal  strength  of 
the  two  portions. 

Now,  a  screw-driver,  or  any  tool  which  must  resist 
a  bending  or  twisting  strain,  must  be  made  in  such  a 
manner  that  the  tension  will  be  taken  up  for  a  con- 
siderable portion  of  the  length  of  the  article,  thus 
doing  away  with  a  tendency  to  break  at  any  one  point. 
In  Fig.  loi,  ^  represents  a  screw  driver  made  in  a  man- 

184 


More  about  screw-drivers. 


ner  that  apparently,  according  to  some  meclianics' 
minds,  will  just  fill  the  bill.  It  is  symmetrical,  that  is, 
there  are  no  breaking  points ;  but  look  at  the  end  that 
enters  the  screw  slot — it  looks  more  like  a  chisel  than  a 
screw-driver.  Now,  when  pressure  is  applied  to  this 
form,  it,  on  account  of  the  inclined  sides, 
slips  out  of  the  slot.     It  will  not  hold,  so 


^ 


Figure  102. 

One  way  of  testing 

a  screw-driver. 


The  Deri-y  CoUard  Cd, 


a   stick   or  piece   of  iron   is 
placed   on  top   of  it  in  the 
form  of  a  lever,  and  one  or 
two  men  hold  down  on  the  end 
of  this,  as  shown  in  Fig.  102, 
and  the  fellow 
doing  the  job  gets 
a  wrench  on,  and 
yanks.    Now,  the 
screw-driver  is 
subjected  to  two 
strains  instead  of 
one.     It  tries  to 
get    out    of    the 
slot,  and  cannot, 

on  account  of  the  power  applied  above.  It  is  also 
subjected  to  torsional  strain  from  the  direct  pull  of 
the  wrench,  and  it  breaks.  Now,  if  it  is  made  of  the 
form  represented  at  <:,  Fig.  10 1,  and  hardened  and  tem- 
pered properly^  there  will  be  very  little  danger  of  it 
breaking  from  any  ordinary  usage. 

When  heating  for  hardening,  give  it  the  lowest  heat 
that  will  produce  the  desired  result.     Remember,  hard- 

185 


Hardening  taper  mandrels. 

ness  is  not  the  desired  quality ;  it  will  not  be  called  on  to 
cut  metals,  it  must  simply  resist  strain  or  pressure, 
consequently  toughness  is  the  quality  to  be  sought. 
Articles  hardened  in  cold  water  do  not  show  this 
quality  to  "such  a  degree  as  those  quenched  in  oil,  so 
it  is  advisable  to  use  oil  as  the  cooling  medium  when  it 
will  answer.  If  oil  will  not  answer,  then  heat  the 
water.  If  it  is  a  comparatively  small  screw-driver, 
heat  the  water  nearly  to  the  boiling  point.  The  larger 
the  article,  the  less  heat  it  will  be  found  necessary  to 
give  the  water ;  but  in  no  case,  unless  the  steel  is  low 
in  carbon  and  the  screw-driver  very  large,  should  cold 
water  be  used. 

The  amount  necessary  to  draw  the  temper  varies 
with  the  percentage  of  carbon  the  steel  contains.  If  it 
is  made  of  ordinary  tool  steel,  it  may  be  heated  until 
hardwood  sawdust  catches  fire  from  the  heat  in  the 
steel,  or  until  a  fine  shaving  from  a  hardwood  stick, 
made  by  drawing  the  stick  across  the  edge  of  the  screw 
driver,  catches  fire,  as  noted  before.  When  the  proper 
temper  shows,  it  may  be  quenched  in  warm  oil  or  hot 
water,  never  in  cold  water. 

While  screw-drivers  may  seem  like  a  small  affair, 
hardly  worth  while  thinking  much  about,  the  frequency 
with  which  they  are  used  and  the  time  lost  in  regrind- 
ing  after  breakage,  make  them  quite  an  important  tool 
in  any  shop.  Then,  too,  the  damaged  screw  heads 
must  be  counted  against  them. 


Tap 


er   Mandrels, 


When  it  is  necessary  to  harden  taper  mandrels 
made  of  tool  steel,  it  is  necessary  to  provide  some  means 
of  uniformly  heating  the  article.     One  end,  being  of  a 

i86 


Hardening  counterbores. 

greater  diameter  than  the  other,  has  a  tendency  to  heat 
slower.  Owing  to  this  fact,  it  will  be  necessary  to 
heat  slowly.  When  it  has  reached  the  desired  heat, 
which  should  be  uniform  throughout,  grasp  by  the 
small  end  with  a  pair  of  tongs  and  immerse  in  a  bath 
of  water  or  brine,  which  has  a  jet  coming  up  from  the 
bottom.  When  it  ceases  singing,  remove  and  plunge 
in  a  tank  of  oil,  allowing  it  to  remain  until  it  is  cooled 
to  the  temperature  of  the  bath.  It  should  then  be 
reheated  to  remove  the  tendency  to  crack  from  internal 
strains. 

Counterbores. 

The  toolmaker  or  designer  should,  when  designing 
tools  that  are  to  be  hardened,  avoid,  as  far  as  possible, 
sharp  corners  between  portions  of  different  sizes.  If 
a  count erbore  is  made  as  shown  in  Fig.  103,  the  presence 


5^'-t-  % 

=\- 

The  Derry  Col  lard  Co. 

Figure  103.     Counterbore  with  square  corners. 

of  sharp  comers  is  an  invitation  for  the  steel  to  crack 
from  unequal  contraction  at  these  points.  If  the 
comers  are  rounded  (filleted),  as  shown  in  Fig.  104,  the 
tendency  to  crack  is  almost  entirely  eliminated. 

Many  times  serious  trouble  arises  from  countersink- 
ing center  holes  too  deeply  in  articles  that  are  to  be 
hardened.  Fig.  104  represents  a  sectional  view  of 
countersinking  in  pilot,  which  is  deep  enough  for  all 

187 


Proper  temper  for  counterbores. 

practical  purposes,  while  in  Fig.  103,  the  countersink- 
ing is  so  deep  that  there  would  be  a  great  tendency  to 
crack  when  hardening.  When  articles  of  this  de- 
scription are  countersunk  too  deeply,  it  is  advisable  to 
fill  the  hole  with  fire-clay  before  placing  it  in  the  fire. 
This  plan,  of  course,  would  not  work  satisfactorily  in 
the  case  of  mandrels,  arbors,  and  similar  tools,  whose 
centers  must  be  hard  in  order  to  resist  wear. 

Heat  to  the  lowest  uniform  red  that  will  cause  the 


%^% 


Figure  104.      Counterbore  with  filleted  corners. 


article  to  harden,  dip  in  a  bath  of  lukewarm  brine, 
hardening  part  way  up  the  portion  necked  below  size 
of  shank. 

When  drawing  the  temper  of  counterbores,  apply 
the  heat  at  shank  end,  allowing  it  to  run  toward  the 
cutting  end  of  teeth. 

The  proper  amount  to  draw  the  temper  depends  on 
the  character  of  the  work  to  be  done,  the  design  of  the 
counterbore,  etc.  It  was  formerly  the  custom  to  draw 
the  temper  to  a  degree  that  made  it  possible  to  sharpen 
the  cutting  edges  by  filing  with  a  sharp,  smooth-cut 
file.  If  the  counterbore  is  made  of  the  design  shown 
in  Fig.  104,  it  may  be  sharpened  by  grinding  on  the 
face  (a)  of  cutting  tooth  with  an  emery  wheel,  thus 
making  it  practical  to  leave  the  tool  much  harder  than 
would  otherwise  be  the  case. 

A  very  common  mistake  when  making  tools  of  this 

188 


Hardening  mandrels,  arbors,  etc. 

description  is  to  stamp  any  distinguishing  marks  on  the 
tool  when  finished,  thereby  springing  it;  and  unless 
this  fact  is  noticed,  the  hardener  will  be  blamed  for  it. 
All  stamping  should  be  done  before  the  important  portions 
are  to  size. 

When  hardening  counterbores  having  inserted  pi- 
lots, it  is  advisable  to  fill  the  pilot  hole  with  fire-clay,  in 
order  to  prevent  the  water  entering.  If  the  design  is 
such  that  the  tool  is  liable  to  crack  when  quenched,  it 
should  be  dipped  in  the  bath  with  the  teeth  uppermost. 
The  contents  of  the  bath  should  be  warmed  to  reduce 
the  liability  of  cracking. 

Hardening  Mandrels,  Arbors,   Etc. 

Mandrels,  arbors,  and  similar  articles,  which  are  to 
be  hardened,  are  generally  made  of  any  piece  of  tool 
steel  which  comes  handy.  Now,  it  is  a  fact  that  tools 
of  this  description  give  a  great  deal  of  trouble  when 
hardened,  unless  the  operator  is  quite  skillful.  As  the 
only  reason  for  hardening  a  mandrel  is  to  give  it  a  hard 
surface  and  make  it  as  stiff  as  possible,  the  desired 
result  may  be  obtained  by  using  a  steel  that  is  not  high 
in  carbon.  Take,  for  instance,  a  steel  containing  ^ 
per  cent,  or  one  per  cent,  carbon.  As  good  results  can 
be  obtained  as  if  a  steel  containing  i  ^  per  cent,  carbon 
were  used,  while  the  article  would  not  be  as  liable  to 
crack  or  spring  as  if  a  high  carbon  were  used. 

When  making  articles  of  this  description,  steel 
somewhat  larger  than  finish  size  should  be  selected. 
The  outside  should  be  turned  off  and  the  piece  annealed. 
After  annealing,  it  may  be  machined  to  grinding  size 
and  then  hardened. 

When  hardening,  a  fire  large  enough  to  heat  the 

189 


Caution  about  small  fire. 

piece  uniformly  should  be  used,  and  the  piece  turned 
frequently  to  insure  good  results.  A  mistake  some- 
times made  in  heating  pieces  of  this  description  con- 
sists in  using  a  fire  too  small  to  accomplish  the  desired 
result.  One  end  and  the  center  is  heated,  the  end  is 
reversed  and  the  opposite  end  is  heated.  The  first 
end,  in  the  meantime,  has  cooled  to  a  degree  that 
makes  it  unsafe  to  quench  the  piece  in  the  bath.  So 
the  second  end  is  heated  hotter  than  it  should  be,  with 
the  idea  in  view  that  the  piece  will  again  be  reversed 
and  the  over-heated  end  will  cool  to  the  proper  harden- 
ing heat,  while  the  temperature  of  the  opposite  end  is 
being  raised  to  the  desired  heat.  When  it  is  taken 
from  the  fire,  it  is  in  the  worst  possible  condition  to 
harden;  the  center  is  too  hot,  one  end  is  apparently 
about  the  right  temperature,  but  the  interior  is  not  hot 
enough.  The  opposite  end  is  possibly  at  about  the 
right  heat,  but  the  interior  is  too  hot.  In  this  condi- 
tion it  is  immersed  in  the  bath  and  violent  strains  are 
set  up,  which  result  in  the  piece  being  cracked  or 
sprung  out  of  shape.  Now,  this  is  not  at  all  right,  yet 
it  is  so  commonly  practiced  that  the  writer  feels  it 
necessary  to  caution  the  reader  against  a  practice  which 
is  so  radically  wrong. 

If  obliged  to  use  an  ordinary  forge,  build  a  fire 
large  and  high  enough  so  the  piece  may  be  uniformly 
heated ;  turn  frequently ;  keep  the  piece  well  buried  in 
the  fire  to  prevent  oxidation  of  the  surface.  When  the 
steel  reaches  a  low  red  heat,  take  it  from  the  fire, 
sprinkle  some  pulverized  cyanide  of  potassium  on  the 
surface.  Place  in  the  fire  and  bring  to  a  uniform  red 
heat,  which  must  be  a  trifle  higher  than  if  there  were 
teeth  or  projections  on  the  surf  ace,  as,  these  being  light, 

190 


Mandrel  centers  must  be  very  hard. 

would  cool  more  quickly  than  a  solid  piece.  If  possi- 
ble, use  a  bath  having  a  jet  of  liquid  coming  up  from 
the  bottom.  If  it  is  a  mandrel,  it  should  be  grasped 
by  one  of  the  ends  with  a  pair  of  tongs  of  the  descrip- 
tion shown  in  Fig.  86.  This  insures  hardening  the 
body  of  the  mandrel,  and  also  allows  the  contents  of  the 
bath  to  have  free  access  to  the  upper  center,  which 
would  not  be  the  case  if  a  pair  of  tongs  of  the  ordinary 
description  were  used. 

It  is  essential  that  the  centers  of  a  mandrel  be  very 
hard.  For  this  reason  a  method  of  quenching  in  the 
bath  should  be  used  that  insures  the  centers  in  both 
ends  hardening. 

If  it  is  considered  best  to  draw  the  temper  of  the 
ends  in  order  to  avoid  the  comers  chipping  or  the  ends 
breaking,  it  is  not  advisable  to  make  them  as  soft  as 
the  dead  center  of  the  lathe,  which  is  usually  drawn  to 
very  deep  straw  or  brown  color.  The  object  attained 
in  having  the  ends  of  a  mandrel  harder  than  the  lathe 
center  is  that  in  case  of  wear,  the  center,  being  the 
softer  of  the  two,  will  probably  wear  rather  than  the 
centers  of  the  mandrel. 

The  piece  should  be  worked  up  and  down  in  the 
bath  until  it  is  of  the  same  temperature  as  the  contents 
of  the  bath,  when  it  may  be  removed  and  heated  some- 
what to  overcome  the  tendency  to  crack  from  internal 
strains.  It  should  be  held  in  a  vertical  position  when 
dipping,  in  order  to  avoid  springing. 

Better  results  will  follow  if  the  piece  is  placed  in  a 
piece  of  pipe  or  tube  when  heating. 

A  very  excellent  method  consists  in  placing  the 
article  in  a  piece  of  gas  pipe,  which  is  closed  at  one 
end.     The  hole  in  the  pipe  should  be  about  one  inch 

291 


Hardening  grooved  rolls. 

larger  in  diameter  than  the  piece  to  be  hardened.  Fill 
around  it  with  granulated  charred  leather,  having  the 
mandrel  in  the  center  of  the  hole  in  the  pipe,  and  the 
ends  should  not  be  within  ^  inch  of  the  ends  of  the 
pipe.  Fill  the  pipe  with  the  charred  leather ;  place  a 
loose-fitting  piece  of  iron  in  the  open  end  of  pipe,  and 
seal  with  fire-clay.  When  this  is  dry,  the  pipe  may  be 
placed  in  the  fire  and  remain  until  the  article  is  uni- 
formly heated  to  the  proper  temperature,  when  it  may 
be  taken  from  the  pipe  and  quenched,  as  described. 

Still  better  results  may  be  obtained  if  the  piece  is 
kept  at  a  low  red  heat  for  a  period  of  several  hours, 
the  time  depending  on  the  size  of  the  piece.  If  j^  inch 
diameter  or  under,  i  ^  hours  will  be  found  sufficient. 
If  larger,  run  correspondingly  longer.  When  it  has 
run  sufficiently  long,  the  piece  may  be  removed  from 
the  tube,  grasped  by  the  tongs,  as  shown,  and  plunged 
in  a  bath  of  raw  linseed  oil,  working  up  and  down 
rapidly  in  the  bath.  This  method  receives  further 
consideration  in  section  on  Pack  Hardening. 

Hardening   Grooved   Rolls. 

When  grooved  rolls  or  similar  articles  are  to  be 
hardened,  it  is  necessary  to  heat  very  uniformly.  The 
projections,  as  shown  in  Fig.  105,  have  a  tendency  to 
heat  faster  than  the  balance  of  the  roll.  Should  they 
become  hotter,  the  projections  will  be  very  liable  to 
crack  or  break  off  when  quenched.  As  it  is  necessary 
to  heat  slowly  in  order  to  get  uniform  heats,  the  piece 
would  be  liable  to  oxidation  on  its  outer  surface,  which 
is  exposed  to  action  of  the  products  of  combustion  in 

19a 


Cooling  in  vertical  position. 

the  fire  and  the  air,  if  heated  in  an  open  fire.  If  small, 
it  may  be  heated  in  a  tube ;  if  too  large  for  this,  it  may 
be  covered  with  the  carbonaceous  paste  described  in 
section  on  Methods  of  Heating.     When  the  article  has 


Th«  Derry  CoUard  Co. 

Figure  105.     A  grooved  roll. 


reached  the  desired  uniform  heat,  it  should  be  plunged 
in  the  bath  in  a  vertical  position.  On  account  of  the 
peculiar  shape  of  the  piece  and  the  tendency  of  the 
steam  generated,  the  contents  of  the  bath  should  be 
agitated  from  the  outside  toward  the  center  of  the  bath. 

A  method  that  gives  very  excellent  results  when 
hardening  articles  of  this  description  is  to  use  a  bath 
having  pipes  coming  up  at  the  sides  of  the  tank,  as 
shown  in  Fig.  io6.  There  should  be  a  sufficient  number 
of  openings  in  these  pipes  to  supply  a  generous  quantity 
of  water  in  order  to  produce  the  desired  result.  The 
water  should  be  under  sufficient  pressure  to  project  the 
contents  of  the  bath  against  the  piece  being  hardened, 
with  enough  force  to  drive  the  steam  away,  so  the 
water  can  readily  come  in  contact  with  the  heated 
surface. 

If  the  pieces  are  short  and  not  too  large,  they  may 
be  heated  in  red-hot  cyanide,  dipping  in  a  bath  of  the 
form  described. 

If  it  is  not  necessary  to  harden  very  deeply,  the 

193 


Hardening  bath  for  grooved  rolls. 

article  may  be  removed  from  the  bath  when  hardened 
sufficiently  and  placed  in  a  tank  of  oil,  leaving  them  in 
the  oil  until  the  steel  is  uniformly  cooled  to  the  tem- 


a 


Q 


W///////M 


Pump 


Q 


The  Derry  CoUard  Co. 


Figure  io6.     Bath  for  hardening  grooved  rolls. 


perature  of  the  oil.  It  is  extremely  important  when 
hardening  pieces  of  this  description  that  they  be 
reheated  as  soon  as  possible  after  removing  from  the 
bath  to  overcome  the  tendency  to  crack  from  internal 
strains.     The  longer  they  remain  under  strain,   the 


194 


Hardening  the  walls  of  holes. 

more  likely  they  are  to  crack  later  without  any  apparent 
cause.     Every  mechanic  can  recall  cases  of  this  kind. 


Hardening  the  Walls   of  Holes. 

A  peculiarity  of  a  cylindrical  piece  of  steel  is  that, 
when  hardened,  it  is  liable  to  become  oval  in  shape. 
This  is  especially  true  of  pieces  having  holes  running 
through  their  centers,  as  shown  in  Fig.  107.     When  it 

is  possible,  or  is 
considered  advis- 
able to  grind  the 
piece  inside  and 
outside  after  hard- 
Figure  107.     Piece  with  hole  through  center.       f^^^^'    ^^®    amOUUt 

it  goes  out  of  shape 
need  not  in  any  way  interfere  with  the  utility  of  the 
tool,  provided  there  has  been  a  sufficient  allowance  of 
stock  made  for  grinding. 

If,  however,  there 
is  no  means  at  hand 
for  grinding  the  piece 
after  hardening,  it  be- 
comes  necessary  to 
harden  in  a  manner 
that  does  away  with 
the  tendency  of  the 
piece  going  out  of 
shape  or  the  hole  con- 


Figure  108.     Gauge  with  hole 
through  center. 


tracting  very  appreciably.     This  may  be  accomplished 
in  the  case  of  such  articles  as  ring  gauges,  reducing 


«95 


No 


necessity  to  "season 


for 


year. 


Figure  109. 
Method  of 

cooling 
ring  gauges. 


dies,   and  any  tools  which  do  not  require  hardening 
on  their  outer  circumference,  if  proper  care  is  taken. 

When  gauges  of  this  description  (as  shown  in  Fig. 
108)  are  hardened  by  the  ordinary  methods,  it  is  neces- 
sary to  rough-grind  them  to  within  a  few  thousandths 

of  an  inch  of  finish  size  and 
lay  them  away  to  "season" 
or  "age."  After  laying  for 
a  few  months  or  a  year,  they 
are  finished  to  size  by  grind- 
ing and  lapping.  It  is  not 
necessary  to  observe  this 
precaution  except  in  the  case 
of  gauges  that  are  to  be  used 
in  making  very  accurate  meas- 
urements. 

Now,  it  is  not  always  de- 
sirable to  wait  a 
year  after  a  piece 
of  work  is  hard- 
ened  before 
grinding  to  size 
and  using.  In 
order  to  o  v  e  r  - 
come  the  tend- 
ency of  altera- 
tion of  sizes  and 
shapes  as  the  piece  ages,  it  may  be  hardened  in  a 
manner  that  gives  the  walls  of  the  hole  sufficient 
hardness  to  resist  wear,  yet  leaving  the  circumfer- 
ence soft.  This  can  be  accomplished  by  heating 
the  piece  very  carefully  to  the  required  heat  and 
placing  in  a  hole  a  trifle  larger  than  the  outside  of  the 

196 


mii 


How  to  close  a  worn  die. 

piece.  Now  place  a  piece  of  metal  having  a  hole  some- 
what larger  than  the  hole  in  the  gauge  on  top  of  the 
piece,  as  shown  in  Fig.  109.  A  stream  of  water  may 
now  be  turned  on  in  such  a  manner  as  to  readily  pass 
through  the  hole,  thus  cooling  the  walls  and  hardening 
them.  The  balance  of  the  stock,  being  protected,  does 
not  harden.  The  walls  of  the  hole  being  hard  and  in- 
flexible do  not  yield  as  the  piece  grows  cold.  And  as 
the  outside  portion  of  the  piece  is  hot  and  yielding,  it 
does  not  necessarily  contract  in  the  direction  of  the 
hole,  thus  reducing  the  tendency  of  alteration  of  size 
of  the  hole. 

Dies  used  for  re- 
ducing the  size  of 
gun  cartridges.  Fig. 
no,    and    similar 


pieces. 


are  hardened 


Figure  no.     Die  for  reducing  cartridges. 


by  this  method,  and 
give  excellent  re- 
sults, because  the 
outside,  being  soft, 
v\rill  have    no    tend- 


ency to  break  from  the  pressure  exerted  when  the 
die  is  in  use. 

As  there  is  very  little  tendency  of  alteration  of  size 
and  shape  of  the  hole,  it  can  be  lapped  to  size  without 
grinding.  In  case  it  is  not  to  be  ground,  there  need 
be  but  a  small  allowance  for  lapping,  provided  the  hole 
is  smooth  and  straight. 

As  is  customary  when  dies  of  this  description  be- 
come worn,  they  may  be  closed  by  heating  red-hot  and 
being  driven  into  a  taper  hole.  This  diminishes  the  size 
of  the  hole  in  the  die,  which  may  then  be  reamed  to  size 


197 


Hardening  where  holes  are  near  edge. 

and  rehardened.  In  order  to  get  good  results,  it  is  ad- 
visable to  anneal  the  steel  after  closing  in,  or  the  mole- 
cules of  steel  will  not  assume  their  proper  relations 
when  hardened. 


Articles  with  Holes  Near  One  Edge. 

When  hardening  articles  having  holes  near  the  edge, 
extreme  care  must  be  observed,  as  the  unequal  con- 
traction occasioned  by  the  form  of  the  piece  will  make 
it  very  liable  to  crack.     A  piece  of  the  form  shown  in 

Fig.  Ill,  represents  an 
example  of  the  form 
mentioned.  While 
such  a  piece  could  be 
hardened  by  the  pack- 
hardening  process 
with  no  liability  of  its 
cracking  if  it  were 
quenched  in  a  bath  of 

Rgurc  III.     Piece  with  hole  near  edge,  ^-^^  j^  ^^^^^  ^^^  ^^^^^^ 

be  considered  advisable  to  use  this  method,  so  it  be- 
comes necessary  to  heat  the  article  in  some  form  of  fire, 
and  quench  in  water. 

The  piece  should  be  heated  very  carefully  and  no 
hotter  than  is  necessary  to  accomplish  the  desired  re- 
sult. It  will  be  necessary  to  use  the  utmost  care  in 
heating,  because  if  the  thin  portion  of  stock  between 
the  hole  and  the  circumference  of  the  ring  were  heated 
any  hotter  than  the  balance  of  the  piece,  it  would 
surely  crack  at  this  point. 

When  dipping  in  the  bath,  the  heavy  portion  should 
198 


How  to  cool  pieces  with  holes  near  edge. 

enter  the  bath  first,  the  thin  portion  should  be  upper- 
most in  order  that  it  may  enter  last. 

If  it  is  not  essential  that  the  walls  of  the  hole  be 
hard,  it  may  be  filled  with  fire  clay,  previous  to  placing 
in  the  fire.  If  treated  according  to  this  method,  the 
danger  of  cracking  is  reduced  to  the  minimum. 

A  method  employed  very  successfully  in  some  shops 
when  hardening  articles  of  this  description,  consists  in 


Figure  112.     Method  for 

holding  piece  with 

hole  near  edge. 


7 


bending  a  piece  of  wire  in  the  form  of  a  hook.  This 
hook  is  heated  red  hot  on  the  bent  end,  and  when  the 
article  is  at  a  uniform  heat,  the  red  hot  end  of  the  hook 
is  inserted  in  the  hole  near  the  edge,  as  shown  in 
Fig.  112,  and  the  article  immersed  in  the  bath.  The 
heavy  portion  will,  of  course,  enter  the  bath  first,  the 
wire  being  red-hot  will  prevent  the  thin  portion  cooling 
as  rapidly  as  it  otherwise  would.  The  size  of  the  wire 
must  be  determined  experimentally;  that  is,  if  many 
pieces  are  to  be  hardened,  the  size  of  wire  that  gives 
best  results  should  be  used,  but  in  no  case  should  it 
fill  the  hole  when  the  pieces  are  cold. 

The  bath  should  be  warmed  somewhat  in  order  to 
reduce  liability  of  cracking. 

Wood -Working  Tools. 

There  are  many  methods  used  in  hardening  tools 
used  for  cutting  wood,  the  different  methods  varying 

199 


Hardening  wood-working  tools. 

according  to  the  nature  of  the  steel  used  and  the  use  to 
which  the  tool  is  to  be  put  when  finished.  The  more 
common  method  is  to  heat  in  an  open  fire  and  plunge 
in  water,  drawing  the  temper  until  the  brittleness  is 
reduced  to  a  point  that  makes  it  possible  for  the  tool 
to  stand  up  when  in  use.  By  this  method,  it  is  neces- 
sary to  draw  the  temper  quite  low  in  order  to  get  a  de- 
gree of  toughness  that  enables  the  tool  to  stand  up  well. 

A  method  that  is  practiced  in  many  shops  is  to  heat 
in  a  muffle  furnace  or  in  a  tube,  hardening  in  a  bath 
of  water  having  oil  on  its  surface,  as  shown  in  Fig.  82, 
the  depth  of  oil  depending  on  the  desired  amount  of 
hardness.  Some  hardeners  claim  to  be  able  to  gauge 
the  amount  of  hardness  by  the  depth  of  oil  to  a  nicety, 
that  makes  it  unnecessary  to  draw  the  temper  after 
hardening.  The  writer  cannot  vouch  for  this  claim, 
as  he  has  never  seen  it  done  when  hardening  wood- 
working tools,  but  has  been  able  to  accomplish  it  when 
certain  kinds  of  iron-working  tools  were  hardened. 

Another  method  consists  in  heating  the  tool  in  a 
crucible  of  red-hot  lead,  or  in  a  crucible  of  red-hot 
cyanide  of  potassium,  dipping  in  a  bath  of  oil,  to  which 
has  been  added  a  quantity  of  alum.  The  exact  amount 
cannot  be  stated,  as  he  has  found  it  to  vary  when 
applied  to  hardening  steels  of  various  percentages  of 
carbon.  The  use  to  which  the  tool  is  to  be  put  when 
hardened,  has  a  great  deal  to  do  with  the  composition 
of  the  bath. 

As  brittleness  is  not  a  desirable  quality  in  wood- 
working tools,  it  is  necessary  to  harden  in  a  manner  that 
insures  toughness  in  the  hardened  product.  For  this 
reason  it  is  not  advisable  to  use  a  bath  of  cold  liquid 
of  any  kind. 


Mixture  for  hardening  wood-working  tools. 

If  the  cutters  are  light  on  the  cutting  portions,  the 
bath  may  be  heated  considerably,  the  temperature  de- 
pending on  the  shape  and  size  of  the  tool  and  the  steel 
used  in  its  construction. 

Various  animal  or  vegetable  oils  are  used  for  quench- 
ing tools  of  this  description,  either  separately  or  mixed 
with  varying  proportions  of  tallow.  Melted  tallow  is 
many  times  used  with  success,  heated  to  a  temperature 
that  gives  good  results  when  applied  to  the  individual 
piece  of  work.  The  amount  necessary  to  draw  the 
temper  depends  on  circumstances  and  can  not  be  arbi- 
trarily stated,  but  it  is  generally  found  to  be  between 
a  brown  and  a  dark  blue  color. 

A  method  employed  in  some  shops  when  hardening 
wood  cutting  tools  consists  in  heating  to  a  low  red 
and  plunging  in  a  mixture  of  molten  lead  and  tin  in 
the  following  proportions :  Lead,  7  parts ;  tin,  4  parts, 
which  melts  at  about  440°  Fahr. 

The  cutters  are  heated  to  a  low  red  and  plunged  in 
this  mixture  at  the  temperature  mentioned,  allowed  to 
cool  for  a  short  time,  then  removed  and  cooled  in  water. 
They  will  be  found  to  be  exceedingly  tough,  and  capa- 
ble of  holding  their  edge  in  a  satisfactory  manner. 

Unless  this  method  is  used  in  a  painstaking  manner, 
it  had  better  not  be  tried,  as  anything  but  satisfactory 
results  will  follow. 

If  many  cutters  are  to  be  hardened,  it  will  be  found 
necessary  to  gauge  the  heat  of  the  bath  by  use  of  a 
thermometer. 

Fixtures   for   Use   in    Hardening. 

In  order  to  attain  certain  results,  it  is  necessary  at 
times  to  make  fixtures  for  holding  the  work.     These 


An  example  of  hardening  fixtures. 

fixtures  are  designed  to  protect  certain  portions  of  the 
piece  of  work  from  the  action  of  the  contents  of  the 
bath. 

The  writer  was  at  one  time  in  charge  of  work  in  a 


] 


The  Derry  Collard  Co. 
Figure  113.      A  hard  piece  to  harden. 


shop  manntacturing  bicycles.  In  order  to  accomplish 
a  desired  object,  the  axle  cones,  which  had  formerly 
been  made  of  machinery  steel,  were  made  from  a  high 
grade  of  tool  steel.     The  front  axle  cone  was  of  the 


^ 


The  Derry  Collard  Co. 

Figure  114.     Device  for  hardening  piece  shown  in  Figure  113. 

shape  shown  in  Fig.  113.  It  was  necessary  to  harden 
the  beveled  portion  extremely  hard,  in  order  to  resist 
wear.  It  was  found  very  difficult  to  harden  this 
portion  without  hardening  the  flange.  If  this  were 
hardened,  it  showed  a  tendency  to  break  when  in  the 
wheel,  as  it  was  very  thin. 

In  order  to  harden  the  bevel  and  leave  the  flange 


The  Genesis  of  pack  hardening. 

soft,  a  fixture  was  made,  as  shown  in  Fig.  114.  The 
cone  was  heated  in  a  crucible  of  red-hot  lead.  When 
it  reached  the  desired  temperature,  the  cover  of  the 
fixture  was  raised  and  the  cone  taken  from  the  lead  by- 
means  of  a  wire  hook  made  for  the  purpose.  It 
was  placed  in  the  fixture,  as  shown,  the  cover  lowered, 
and  the  fixture  immersed  in  a  bath  of  water,  working 
it  around  well  until  the  cone  was  cold,  when  the  fixture 
was  inverted  over  a  tank  of  boiling  water,  and  the  cone 
dropping  into  this  and  remained  until  a  sufficient 
quantity  was  in  the  catch  pan.  Fig.  45,  to  warrant 
emptying  it.  This  tank  was  found  very  valuable,  as 
it  furnished  a  means  whereby  the  strains  incident  to 
hardening  could  be  removed,  and  at  the  same  time  the 
temper  was  drawn  sufficiently. 


Pack  Hardening. 


When  articles  which  are  small  or  tkln  are  heated  to 
a  red  and  plunged  in  oil,  they  become  hard  enough  for 
most  purposes,  but  not  as  hard  as  if  immersed  in  water. 
Articles  hardened  in  oil  seldom  crack  from  the  effects 
of  cooling,  as  the  heat  is  not  absorbed  as  quickly  as  if 
water  were  used,  neither  are  they  as  likely  to  spring. 

The  fact  that  articles  quenched  in  oil  showed  no 
tendency  to  crack,  and  very  little  liability  to  spring, 
has  led  the  writer  to  make  exhaustive  experiments  in 
perfecting  a  method  whereby  articles  which  gave 
trouble  when  hardened  by  ordinary  methods  might  be 


Pack  hardening  prevents  cracking. 

hardened  in  oil  and  produce  a  surface  as  hard  as  if  it 
were  heated  red-hot  and  plunged  in  water.  The  re- 
sults have  been  more  gratifying  than  were  ever  dream- 
ed of  before  trying.  It  is  not  claimed  that  this  method 
was  originated  by  the  writer.  It  was  suggested  by  a 
man  in  his  employ,  who  had  seen  it  practiced  with 
varying  results  in  a  shop  where  he  formerly  worked. 

The  fact  that  milling  machine  cutters,  punch  press 
dies,  and  similar  articles,  could  be  treated  in  such  a 
manner  that  they  might  be  hardened  in  oil  without 
danger  of  cracking,  led  to  experimenting,  which  re- 
sulted in  a  method  whereby  tools  could  be  hardened 
with  absolutely  no  danger  of  cracking.  The  tendency 
to  spring  was  also  reduced  to  the  minimum.  Unexpected 
results  were  accomplished  in  some  ways,  for  it  was 
found  by  experience  that  milling  machine  cutters  could 
be  run  at  a  periphery  speed,  two,  and  in  some  cases  four, 
times  as  great  as  when  a  similar  cutter  made  from  the 
same  bar  was  heated  red-hot  and  plunged  in  water. 
Punch  press  blanking  dies  would  do  from  six  to  ten 
times  the  amount  of  work  as  when  hardened  by  meth- 
ods formerly  used. 

It  was  also  found  extremely  satisfactory  when  ap- 
plied to  taps  and  screw  thread  dies,  because  the  tendency 
to  alteration  of  pitch  was  reduced  to  the  least  possible 
amount.  Neither  would  they  change  so  far  as  diametri- 
cal measurements  were  concerned.  Gauges  hardened 
by  this  method  gave  results  fully  as  satisfactory  as  other 
articles  hardened  in  a  similar  manner.  Long  reamers, 
stay-bolt  taps,  and  similar  tools,  have  been  hardened 
by  the  thousands  and  shown  results  more  than  satis- 
factory. 

Tool  steel  is  made  with  a  sufficient  quantity  of 

ao4 


Never  use  bone  in  pack  hardening. 

carbon  to  harden  in  a  satisfactory  manner  and  accom- 
plish the  results  intended  when  the  tool  is  made.  To 
make  steel  with  a  higher  percentage  of  this  hardening 
element,  and  put  it  on  the  market,  would  be  folly,  as 
the  average  man  hardening  steel  would  treat  it  the 
same  as  the  ordinary  tempers  are  treated,  with  the  re- 
sult that  the  tools  made  from  it  would  be  ruined  when 
hardened. 

Now,  tool  steel  may  be  treated  with  carbonaceous 
materials  when  red-hot,  with  the  result  that  the  sur- 
faces will  be  extremely  hard  if  the  article  is  quenched 
in  oil.  The  depth  of  the  hardened  surface  depends  on 
the  length  of  time  the  article  is  subjected  to  the  car- 
bonizing element.  In  order  to  accomplish  the  desired 
result,  the  piece  of  work  must  be  packed  in  a  hardening 
box  with  the  carbonaceous  material;  the  top  must  be 
closed  with  a  cover  slightly  smaller  than  the  opening 
in  the  box,  and  the  space  between  the  cover  and  sides 
of  the  box  covered  with  fire-clay.  This  operation  is 
familiarly  known  as  sealing.  Sealing  the  box  has  the 
effect  of  preventing  the  gases  escaping.  It  also  pre- 
vents the  direct  heat  of  the  fire  from  entering  the  box, 
as  that  would  be  very  injurious  to  the  steel.  Then 
again,  the  oxygen  in  the  air  is  excluded  from  the  box, 
or,  if  present  in  a  degree,  does  not  oxydize  the  surface 
of  the  piece,  as  it  is  taken  up  by  the  packing  materials 
in  the  box. 

It  is  very  necessary  when  charging  steel  by  the 
process  under  consideration,  that  a  carbonizing  ma- 
terial be  used  which  contains  no  elements  injurious  to 
tool  steel.  For  this  reason  no  form  of  bone  should 
ever  be  used,  as  bone  contains  a  very  high  percentage 
of  phosphorus,   and  phosphorus,  when  present  in  tool 

205 


About  boxes  for  pack  hardening. 

steel,  has  the  effect  of  making  it  extremely  brittle.  The 
processes  the  steel  maker  puts  the  steel  through  in 
order  to  remove  injurious  impurities  is  one  reason  of 
its  high  cost  as  compared  with  the  ordinary  cheap 
grades  of  steel.  The  lower  the  percentage  of  phos- 
phorus, the  more  carbon  it  is  safe  to  have  in  the  steel ; 
so  it  will  readily  be  seen  that  any  process  which  results 
in  an  addition  of  this  harmful  impurity  should  never 
be  used.  The  writer  has  used  a  mixture  of  equal  parts, 
by  measure,  of  granulated  charcoal  and  granulated 
charred  leather  in  most  of  his  work  for  the  past  nine  or 
ten  years  with  the  best  results ;  although  in  exceptional 
cases,  where  extreme  hardness  was  desired,  charred 
leather  alone  was  used. 

The  work  is  packed  in  a  hardening  box.  This  box 
may  be  either  wrought  iron  or  cast  iron.  Best  results 
are  claimed  by  some  when  wrought  iron  boxes  are  used. 
But  the  writer  has  never  in  practice  been  able  to  notice 
any  difference,  so  he  has  used  cast  iron  boxes  altogether 
for  the  past  eight  years,  as  they  are  cheaper  and  more 
readily  obtained.  The  work  should  be  placed  in  the 
box  in  a  manner  that  does  not  allow  any  of  the  pieces 
to  come  within  i  }^  inches  of  the  bottom  or  top  of  the 
box,  or  within  1%  to  i^  inches  of  the  sides  or  ends,  for 
two  reasons.  If  they  are  placed  too  near  the  walls  of 
the  box,  they  are  affected  by  every  change  of  tempera- 
ture in  the  furnace.  Then  again,  cast  iron  has  a  great 
affinity  for  carbon,  and  will  extract  it  from  a  piece  of 
tool  steel  if  it  comes  in  contact  with  it.  If  one  end  of 
an  article,  packed  as  described,  comes  in  contact  with 
the  walls  of  the  box,  the  piece  will  not  harden  at  that 
point,  or,  if  it  does,  it  will  not  be  as  hard  as  the  balance 
of  the  piece.     And,  as  a  chain  is  no  stronger  than  its 

»o6 


How  to  pack  for  hardening. 

weakest  link,  so  a  hardened  tool  is  no  better  than  its 
softest  spot,  provided  it  is  on  any  cutting-  portion,  be- 
cause, when  that  dulls,  the  whole  tool  must  be  ground. 

This  method  of  pack  hardening  is  not  only  a  means 
of  getting  good  results,  but  when  work  is  hardened  in 
large  quantities,  it  is  a  much  cheaper  method  than  that 
ordinarily  used,  because  quite  a  number  of  pieces  may 
be  packed  in  the  box  at  a  time.  Or,  if  the  furnace  used 
is  of  sufficient  capacity,  several  boxes  may  be  heated  at 
the  same  time. 

When  packing  work  in  the  hardening  box,  place 
about  i>^  inches  of  packing  material  in  the  bottom,  then 
lay  a  row  of  work  on  this,  being  careful  that  no  pieces 
come  within  ^  inch  of  each  other,  or  within  i  Yz  inches 
of  the  walls  of  the  box.  Cover  this  row  of  work  with 
packing  material  to  the  depth  of  ^  inch,  put  in  another 
row  of  work,  and  continue  in  this  way  until  within  i  % 
inches  of  the  top  of  the  box.  After  covering  each  row 
of  work  with  the  packing  material,  it  should  be  tamped 
down  lightly  to  insure  its  staying  in  place.  When  the 
box  is  filled  to  within  the  distance  of  top  mentioned 
(i}^  inches),  the  balance  should  be  filled  with  packing 
material,  the  cover  put  in  place  and  sealed  with  fire- 
clay mixed  with  water  to  the  consistency  of  dough, 
and  allowed  to  dry  before  placing  in  the  furnace. 

Before  the  articles  are  packed  in  the  box,  a  piece  of 
iron  binding-wire  should  be  attached  to  each  piece  of 
work  in  such  a  manner  that  the  article  may  be  removed 
from  the  box  and  dipped  in  the  bath  by  this  means, 
unless  the  piece  is  too  heavy  to  be  handled  in  this  man- 
ner, in  which  case  it  must  be  grasped  with  a  pair  of 
tongs.  The  wires  should  extend  up  the  sides  to  the 
top   of    the    box    and  hang  over  the   edge,  in   order 

ao7 


Figure  115.     The  wrong  way  to 
pack  harden. 


Pack  boxes  with  similar  articles. 

that  the  operator  may  readily  see  them  when  removing 

the  articles  from  the  box.     If  several  rows  of  work  are 

placed  in  the  box,  it  is  necessary  to  place  the  wires  in 

a  manner  that  allows  the  different  rows  to  be  readily 

distinguished.     As  it  is  necessary  to  draw  the  pieces  on 

the  top  row  first,  each  succeeding  row  should  be  drawn 

in  its  order,  because  if  an  article  were  drawn  from  the 

bottom  row  first,  it  would  probably  draw  one  or  more 

of  the  pieces  located  above  along  with  it.     As  a  conse- 

quence  they 

would   lay   on 

the  top   of  the 

box  exposed  to 

the  action  of  the 

air,   and   would 

cool  perceptibly 

while    the    first 

piece  was  being 

quenched  in  the 

bath.     For  this   reason  it   is   advisable  to  draw  the 

pieces  in  the  top  row  first,  as  described. 

As  the  length  of  time  a  piece  of  steel  is  exposed  to 
the  carbonaceous  packing  material  after  it  is  red-hot 
determines  the  depth  of  hardening,  articles  packed  in 
a  box  should  all  be  of  a  character  that  need  carbonizing 
alike,  or  some  pieces  will  not  receive  a  sufficient  depth 
of  carbonizing  and  others  will  receive  too  much.  Know- 
ing this,  one  may  select  the  articles  accordingly,  pack- 
ing those  requiring  charging  for  one  hour  in  one  box, 
those  requiring  two  hours  in  another,  and  so  on.  A 
little  experience  will  teach  one  the  proper  length  of 
time  to  give  a  tool  of  a  certain  size  to  accomplish  a 
given  result. 


The  Derry-Collard  Co. 


ao8 


Boxes  for  pack  hardening. 

Attention  must  be  paid  to  the  shape  of  the  piece 
when  packing  in  the  box.  If  it  is  long  and  slender,  it 
should  not  be  packed  in  such  a  manner  that  it  will  be 
necessary  to  draw  it  through  the  packing  material,  as 
shown  in  Fig.  115,  or  it  will  surely  spring  from  doing 
so,  it  being  red-hot,  and  consequently  easily  bent.  If 
but  a  few  pieces  of  this  character  are  to  be  hardened, 
it  would  not  be  advisable  to  procure  a  box  especially 


Figure  Ii6.      Box  for  pack  hardening. 


adapted  to  it.  In  that  case  the  articles  could  be  packed 
two  or  three  in  a  box.  When  they  have  run  the  proper 
length  of  time,  the  box  should  be  removed  from  the 
furnace,  turned  bottom  side  up  on  the  floor,  provided 
the  floor  is  of  some  material  that  will  not  catch  fire. 
The  piece  of  work  may  be  pulled  out  lengthwise  from 
the  mass,  and  in  that  way  all  danger  of  springing  is 
done  away  with. 

If,  however,  quite  a  number  of  pieces  are  to  be 
hardened,  it  is  advisable  to  procure  a  box  adapted  to 
pieces  of  this  description.  This  may  be  done  by  adopt- 
ing a  design  opening  at  the  end,  as  shown  in  Fig.  n6. 
This  may  stand  on  end  with  the  opening  uppermost 
while  packing  the  pieces.     If  a  furnace  of  the  design 

209 


How  to  tell  when  heated. 


shown  in  Fig.  1 1 7  is  available,  it  should  be  used,  as  the 
box  can  stand  on  end.  If  this  form  of  furnace  is  not 
at  hand,  the  box  may  be  placed  on  its  side  in  any  fur- 
nace large  enough  to  receive  it.  If  necessary  to  use  a 
furnace  where  the  box  must  lay  on  its  side,  it  will  be 
advisable  to  provide  some  way  of  fastening  the  cover 
in  place.  This  may  be  done 
by  drilling  a  j^  inch  hole  on 
opposite  sides  of  the  box  and 
running  a  rod  at  least  -jV  of 
an  inch  smaller  than  the  hole 
across  the  face  of  the  cover, 
Fig.  118,  before  sealing  with 
fire-clay.  This  rod  can  easily 
be  removed  when  the  articles 
are  ready  for  immersion  in 
the  bath. 

In  order  that  the  exact 
time  at  which  the  work  be- 
comes red-hot  may  be  ascer- 
tained, it  will  be  necessary 
to  use  test  wires.     Several  % 
inch   holes    may    be   drilled 
near  the  center  of  the 
cover,    a  -f^    inch  wire 
run  through  each  of 
these  holes  to  the  bot- 
tom  of  the  box,   as 


The  Derry  Collard  Co. 

Figure  117.     Furnace  for  use  in 
pack  hardening. 


shown  in  Fig.  26.  When 
the  work  has  been  in 
the  furnace  for  a  sufficient  length  of  time  to  become 
heated  through,  according  to  the  judgment  of  the 
.  operator,  one  of  the  test  wires  may  be  drawn  and  its 


The  length  of  time  work  should  be  run. 

condition  noted.     If  it  shows  red-hot  the  entire  length, 
note  the  time.     If  not,   wait  a  few  minutes  (say,    15 
minutes)  and  draw  another  wire.     When  one  is  drawn 
that  shows  the  proper  temperature,  time  from  this. 
The  length  of  time  the  pieces  should  be  run  cannot 


The  Derry  Colliwd  Co. 

Figure  118.     Method  of  fastening  cover  in  place. 

be  Stated  arbitrarily,  as  the  character  of  the  work  to  be 
done  by  the  tool  must,  in  a  measure,  determine  this. 
However,  if  the  pieces  are  ^  inch  diameter,  and  are  to 
cut  a  soft  grade  of  machinery  steel,  one  hour  may  be 
found  sufficient.  If  a  harder  surface  is  required,  it  is 
necessary  to  run  somewhat  longer  (say,  1%  hours). 
When  the  work  has  run  the  required  length  of  time,  the 
box  may  be  removed,  the  cover  taken  off,  and  the  ar- 
ticles taken  out  one  at  a  time  and  dipped  in  a  bath  of 
raw  linseed  oil.  When  the  articles  are  long,  it  is  ad- 
visable, if  possible,  to  use  a  bath  having  a  perforated 
pipe  extending  up  two  opposite  sides  of  the  tank,  as 
shown  in  Fig.  119.  A  pump  should  be  connected  with 
the  oil  in  the  bath,  pumping  it  through  a  coil  of  pipe 
in  a  tank  of  water  and  forcing  back  into  the  tub  through 
the  upright  perforated  pipes  shown.  This  method 
insures  evenly  hardened  surfaces,  as  the  jets  of  oil 
forced  against  the  sides  of  the  article  drive  the  vapors 
away  from  the  piece,  thus  insuring  its  hardening.  It 
is  necessary  to  move  the  work  up  and  down  and  to  turn 


How  to  treat  milling  cutters. 

it  quarter  way  around  occasionally  in  order  to  present 
all  sides  to  the  action  of  the  oil. 

When  milling  machine  cutters,  or  similar  tools 
having  projections,  are  to  be  hardened  by  this  method, 
they  should  be  packed  in  the  box,  using  the  packing 


Figure  119.      Bath  for  use  in 
pack  hardening. 


Tbe  Deny  Collard  Co. 


material  mentioned.  Previous  to  placing  the  cutters 
in  the  hardening  box,  a  piece  of  iron  binding- wire  should 
be  attached  to  each  cutter  and  allowed  to  project  over 
the  edge  of  the  box.  Test  wires  should  be  run  down 
through  the  holes  in  the  cover,  as  shown  in  Fig.  26. 
The  length  of  time  the  cutters  should  run  is  determin- 
ed by  the  character  of  the  work  they  are  to  do ;  but  for 


Milling  cutters  needing  no  tempering. 

ordinary  milling,  a  cutter  3  inches  diameter,  if  of  the 
ordinary  design,  should  run  about  3  hours. 

If  the  teeth  are  heavy,  of  the  style  known  as  form- 
ed mills,  Fig.  120,  they  should  be  run  4  hours  after  they 
are  red-hot.  When  the  box  is  removed  from  the  fur- 
nace, the  cutters  may  be  removed  one  at  a  time,  placed 
on  a  bent  wire  of  the  form  shown  in  Fig.  81,  and  im- 
mersed in  the  oil,  working  them  around  well  until  all 
trace  of  red  has  disappeared,  when  they  may  be  dropped 
to  the  bottom  of  the  bath  and  left  until  cold. 

A  milling  machine  cutter  of  the  form  shown  in  Fig. 
120  will  not  as  a  rule  require  tem- 
pering. The  teeth  may  be  left 
as  hard  as  they  come  from  the 
bath,  but  those  of  the  ordinary 
form  of  tooth  should  have  the  tem- 
per drawn.  This  may  be  done  by 
the  method  described  under  Hard- 
ening and  Tempering  Milling 
Machine  Cutters,  or,  if  there  are 

.         .  The  Derry  ColUrd  Co. 

many  cutters,   a   savmg  of   time 

will    result    if    the    articles    are  igure  12,0.      orme 

-1     •  -I         1  f       '^  11  milling  cutter. 

placed  m  a  kettle  of  oil  and  the 

temperature  gauged  by  a  thermometer,  drawing  them 

to  430  degrees. 

Punch  press  blanking  dies  give  excellent  satisfac- 
tion if  hardened  in  this  manner.  The  die  is  packed  in 
a  box.  Test  wires  are  run  down  through  the  opening 
in  the  die  to  the  bottom  of  the  box.  "When  drawing  the 
wires  to  test  the  heat,  do  not  draw  them  way  through 
the  cover.  After  observing  the  heat,  place  the  wire 
back  in  its  original  position.  A  wire  can  be  raised  from 
time  to  time,  the  amount  of  heat  observed  and  the  wir^ 

213 


Treatment  of  blanking  dies. 

returned.  In  this  way  the  operator  can  tell  from  time  to 
time  the  exact  temperature  of  the  piece  being  heated, 
and  as  the  same  laws  governing  the  heating  of  steel  in 
the  open  fire  apply  when  heating  to  harden  by  this 
method,  it  is  advisable  to  keep  the  heats  as  low  as  pos- 
sible ;  for  steel  treated  by  this  method  will  harden  in 
oil  at  a  lower  heat  than  if  treated  in  the  ordinary  way 
and  hardened  in  water. 

Blanking  dies  for  the  class  of  work  usually  done 
on  punch  presses  (if  they  are  i  inch  to  i  j^  inches  thick) 


Figure  121.      Bath  for 
blanking  dies. 


vx/i>)<;>./^y/yyyyx^z^xy^^^y^yyy^///yy/x^^^^^ 


Tlie  Perry  Collard  Co. 

should  run  about  four  hours  after  they  are  red-hot. 
At  the  expiration  of  that  time  the  box  may  be  removed 
from  the  furnace,  the  die  grasped  by  one  end  with  a 
pair  of  tongs  and  immersed  endwise  down  into  a  bath 
of  raw  linseed  oil.  It  is  a  good  plan  to  have  the  bath 
rigged  as  shown  in  Fig.  121.  A  pipe  is  connected  with 
the  tank  near  the  top,  and  runs  in  a  coil  through  a  tank 
of  water.  A  pump  draws  the  oil  from  the  tank  through 
the  coil,  and  forces  it  back  into  the  bath,  as  represented. 


214 


Handling  of  dies  and  taps. 


The  inlet  pipe  may  be  so  situated  as  to  cause  the  oil  to 
circulate  with  considerable  force  through  the  bath.  This, 
striking  the  face 
of  the  die,  passes 
through  the 
opening,  insures 
good  results.  If 
no  means  are  pro- 
vided for  the  cir- 
culation of  the 
oil,  the  die  may- 
be swung  back 
and  forth  in  the 
oil,  and  it  will 
harden  in  a  satis- 
factory manner. 
Forming  and 
bending  dies,  if 
hardened  by  this 


The  Derry  Collard  Co. 

Figure  1 22.     One  method  of  packmg 
snap  gauges. 


method,  must  be   run  longer,  and  heated  somewhat 
hotter,  yet  not  hot  enough  to  injure  the  steel. 

Pack  hardening  fur- 
nishes  a  method 
whereby  taps  may  be 
hardened  without 
altering  the  pitch  very 
perceptibly;  neither 
will  the  diametrical 
measurements  be 
changed,  provided  the 
blanks  were  annealed  after  blocking  out  to  shape,  and 
by  this  method  the  teeth  are  made  exceedingly  hard 
without  being  brittle.     A  tap  from  one  to  two  inches 


Figure  123. 


Another  method  of  packing 
snap  gauges. 


215 


Pack  hardening  for  gauges. 

in  diameter  should  be  run  about  two  hours.  It  should 
be  worked  around  rapidly  in  the  bath,  in  order  that  the 
teeth  may  be  hardened.  For  general  machine  shop 
work,  taps  do  not  require  the  temper  drawn  as  low 
as  if  they  were  hardened  by  heating  red-hot  and 
plunging  in  water.  Generally  speaking,  430  degrees 
(a  faint  straw  color)  is  sufficient,  provided  a  low  heat 
was  maintained  in  the  furnace. 

This  is  an  ideal  method  of  hardening  gauges  and 
similar  work,  as  the  liability  of  cracking  is  eliminated 
and  the  danger  of  springing  is  reduced  to  the  minimum. 
If  the  gauge  is  of  the  plug  or  ring  form,  it  is  not  neces- 
sary to  allow  as  great  an  amount  for  grinding  as  would 
otherwise  be  the  case,  as  there  is  little  danger  of 
springing. 

When  hardening  snap  gauges,  especially  if  they 
are  long,  it  is  advisable  to  pack  as  represented  in  Fig. 
122,  provided  a  box  deep  enough  is  at  hand.  If  obliged 
to  pack  in  a  box  so  that  the  gauges  lay  lengthwise  in 
the  box,  they  should  be  so  placed  as  to  have  the  edges 
up  and  down,  as  shown  in  Fig.  123,  thus  doing  away 
with  the  tendency  to  spring  when  they  are  drawn 
through  the  packing  material. 

Articles  of  a  form  which  betokens  trouble  when 
hardening  can,  if  proper  precautions  are  taken,  be 
hardened  by  this  method  in  a  very  satisfactory  manner. 
Take,  for  instance,  the  shaft  shown  in  Fig.  124.  This 
was  made  of  ^  per  cent,  carbon  crucible  steel,  and  turned 
within  a  few  thousandths  of  an  inch  of  finish  size.  It 
was  packed  in  a  mixture  of  charred  leather  and  char- 
coal, and  subjected  to  heat  for  i^  hours  after  it  was 
red-hot.  It  was  then  dipped  in  a  bath  of  raw  linseed 
oil,    heated   to  a  temperature   of  90°.     It  was  found 

zi6 


Treating  difficult  subjects. 

upon  being  tested   between    centers    to    run    nearly- 
true. 

The  designer  does  not  always  take  into  consideration 
the  difficulties  which  may  be  encountered  when  a  piece 
of  irregular  contour  is  hardened,  consequently  we  some- 
times run  across  articles  which  call  for  serious  study 
on  the  part  of  the  hardener  when  the  article  reaches 
him.     Then  again,  such  articles  are  many  times  made 


The  Derry  Collard  Co. 

Figure  124,      A  peculiar  piece  to  harden. 

of  a  high  carbon  tool  steel,  when  a  low  grade  steel  would 
answer  the  purpose  as  well,  and  not  cause  nearly  as 
much  trouble. 

At  one  time  the  writer  was  called  to  a  shop  where 
they  were  experiencing  all  kinds  of  trouble  in  an  attempt 
to  harden  a  gauge  of  the  description  shown  in  Fig.  125. 
As  it  was  not  practical  to  grind  the  interior  of  this  gauge 
with  a  grinding  machine,  it  was  necessary  that  it  should 
retain  its  shape  when  hardened.  In  order  to  accom- 
plish this,  the  gauge  was  surrounded  with  a  mixture  of 
fire-clay,  to  which  was  added  sufficient  hair  (obtained 
from  a  plasterer)  to  hold  it  together.  It  was  moistened 
with  water  to  the  consistency  of  dough.  The  hole  in  th  e 
gauge  was  filled  with  finely  granulated  charred  leather. 

It  was  then  placed  in  a  small  hardening  box, in  the 
bottom  of  which  was  placed  2  inches  of  granulated  wood 

ai7 


How  the  "teaser"  was  hardened. 

charcoal.     The  box  was  filled  with  charcoal,  the  cover 
placed  in  position,  and  sealed  with  fire-clay. 

The  box  was  subjected  to  heat  for  one  hour  after 
the  contents  were  red-hot,  this  being  ascertained  by 
means  of  the  test  wires,  as  described.     The  gauge  was 

then   taken    from 


the  box,  the  leather 
removed  from  the 
hole,  and  a  jet  of 
raw  linseed    oil 


Figure  125. 

A  "teaser"  for 

hardening. 


TheDerry  CoUard  Co. 


forced  through  the  hole  until  the  piece  had  cooled  off. 
The  walls  of  the  hole  were  very  hard,  and  the  gauge 
was  found  by  test  to  have  retained  its  shape.  The 
coating  of  fire-clay  prevented  the  exterior  hardening 
of  the  piece,  thereby  eliminating  the  tendency  to 
spring  or  go  out  of  shape.  The  walls  of  the  hole, 
hardening  first,  retained  their  shape,  and  the  balance, 
being  red-hot,  conformed  to  this  portion. 

While  it  would  be  impossible  to  enumerate  the 
various  articles  of  irregular  contour  that  may  be  hard- 
ened by  applying  this  principle — namely,  protecting 
the  portions  that  do  not  require  hardening,  by  the  use 
of  a  mixture  of  fire-clay  and  water,  adding  sufficient 
hair  to  hold  it  together — it  can  safely  be  said  that  many 
thousand  dollars'  worth  of  tools  are  ruined  annually, 
which  might  have  been  saved  had  this  precaution  been 
observed. 


zi8 


Pack  hardening  for  mandrels  and  arbors. 

As  this  process  of  charging  the  surface  of  the  steel 
with  carbon  is  a  process  of  cementation,  it  is  necessarily- 
slow.  When  extremely  high  carbon  steel  is  used  in 
making  tools,  it  is  considered  advisable  by  some  to  use 
hoofs  and  horns  as  packing  material  rather  than  leather. 
At  times  it  is  not  considered  desirable  to  subject 
the  articles  to  heat  for  so  great  a  length  of  time.  In 
such  cases  it  is  necessary  to  treat  the  surfaces  to  be 
hardened  with  some  material  that  will  act  more  quickly 
than  charred  leather.  In  fact,  at  times  it  is  necessary 
to  prevent  any  portion  other  than  the  ones  to  be  hard- 
ened from  becoming  red-hot. 

This  can  be  effected  by  covering  the  parts  with  the 
fire-clay  mixture  to  a  considerable  depth,  applying  heat 
to  the  portions  that  need  hardening.  When  it  is  not 
desirable  to  subject  the  article  to  heat  for  a  length  of 
time  sufficient  to  charge  the  steel  with  the  necessary 
amount  of  carbon  to  cause  it  to  harden  (if  it  was  to  be 
carbonized  by  means  of  charred  leather),  excellent  re- 
sults may  be  had  by  the  use  of  a  mixture  of  5  parts  of 
rye  flour,  5  parts  table  salt,  2  parts  yellow  prussiate  of 
potash,  filling  the  hole  or  covering  the  portions  to  be 
hardened  with  this. 

Mandrels,  or  any  form  of  arbor  which  it  is  consid- 
ered advisable  to  harden,  will  harden  in  a  more  satis- 
factory manner  by  this  method  than  by  any  that  has 
come  to  the  writer's  notice.  If  the  article  is  long  and 
slender,  do  not  pack  in  the  box  in  such  a  manner  that 
they  will  spring  when  drawn  out ;  but  if  the  shape  of 
the  box  is  such  that  this  cannot  be  avoided,  the  box 
may  be  turned  bottom  side  up  on  the  floor  when  the 
articles  are  ready  for  hardening,  as  previously  explained. 
If,  however,  the  mandrels  are  made  of  the  proportions 

119 


How  to  dip  mandrels  and  arbors. 


tisually  observed  when  making  for  general  shop  usd, 
there  is  very  little  liability  of  springing  when  drawing 
them  through  the  packing  material.  The  mandrel  may 
be  wired  as  represented  in  Fig.  126,  or  it  may 
be  grasped  with  a  pair  of  tongs  of  a  form  that 
allows  the  contents  of  the  bath  to  have  ready 
access  to  the  end  of  piece ;  but  as  tongs  of  this 
form  are  not  in  general  use,  the  wires  will 
answer  unless  the  pieces  are  very  heavy.  In 
this  case  it  is  advisable  to  procure  tongs  of 
a  suitable  shape  rather  than  to  have  an  un- 
satisfactory article  when  it  is  finished.  As 
stated  under  Examples  of  Hardening,  it  is 
never  advisable  to  hold  a  mandrel  with  any 
form  of  tongs  that  in  any  way  interfere  with 
the  hardening  of  the  walls  of  centers  in  the 
ends  of  a  mandrel. 

If  the  work  is  wired,  it  should  be  done 
in  a  manner  that  makes  it  possible  to  dip 
the  mandrel  in  the  bath  in  a  vertical  position, 
to  avoid  any  tendency  to  spring.  The  wires 
may  be  grasped  by  means  of  tongs  which 
close  together  very  nicely,  as  shown  in  Fig. 
126,  in  order  that  they  may  not  lose  their 
grip  and  the  piece  fall  to  the  bottom  of  the 
bath  before  the  red  had  disappeared  from 
the  surface.  It  should  be  worked  up  and 
down  in  the  oil  until  all  trace  of  red  has 
disappeared,  when  it  may  be  lowered  to  the  bottom 
and  left  until  cooled  to  the  temperature  of  the  bath. 

Circular  forming  tools,  especially  those  having 
long,  slender  projections  and  sharp  comers,  as  shown 
in  Fig.  127,  are  safely  hardened  by  this  process,  as  they 


n  r 


Stay-bolt  taps  and  the  like. 

can  be  given  any  degree  of  hardness  desirable  without 
making  them  brittle.  Being  solid  in  form,  they  must 
be  heated  for  a  longer  period  of  time  than  if  there  were 
teeth  on  the  surface — as  a  milling  machine  cutter.  As 
with  other  cutting  tools,  the  length  of  time  a  tool  of 
this  form  should  be  subjected  to  heat  depends  on  the 

nature  of  work  to 
be  performed  by 
it.  A  tool  4  inches 
in  diameter  and  2 
inches  wide  for 
ordinary  work 
should  run  about 
4  hours  after  it  is 
red-hot.  If  there 
are  slender  projec- 
tions from  the  face  of  the  tool,  it  will  be  found 
necessary  to  draw  the  temper  somewhat ;  but  as  a  rule 
it  should  not  be  drawn  as  low  as  if  it  were  hard- 
ened by  the  methods  ordinarily  employed. 

The  writer  has  in  mind  a  forming  tool  of  the 
same  general  outline  as  the  one  represented  in  Fig.  127, 
which  gave  excellent  results  when  drawn  to  350  degrees 
after  hardening  by  the  method  under  consideration. 
It  was  hard  enough  to  stand  up  in  good  shape,  and  yet 
tough  enough  to  stand  very  severe  usage. 

If  the  formed  surface  is  of  a  shape  that  insures 
strength — that  is,  if  there  are  no  projections — the  cut- 
ter should  be  left  as  hard  as  when  it  comes  from  the 
bath. 

Stay-bolt  taps  and  similar  tools  may  be  packed  in 
a  box  of  the  proper  shape  and  run  for  a  length  of  time, 
depending  on  the  size  of  the  piece.     They  should  then 


Tlw  Derry  Collard  Co, 

Figure  127.     A  forming  tool. 


221 


Precautions  to  be  taken  on  large  work. 

be  taken  one  at  a  time  and  immersed  in  a  bath  of  raw 
linseed  oil  and  worked  up  and  down  in  a  vertical  man- 
ner, moving  to  different  parts  of  the  bath,  unless  there 
is  a  jet  of  oil  coming  up  from  the  bottom.  Or,  better 
still,  having  perforated  pipes  coming  up  the  sides  of 
the  bath,  as  represented  in  Fig.  119.  In  either  case  it 
is  advisable  to  work  the  articles  up  and  down,  to  avoid 
the  vapors  which  always  have  a  tendency  to  keep  the 
contents  of  the  bath  from  acting  on  the  heated  steel. 

If  the  articles  are  long,  a  deep  tank  should  be  used 
for  the  bath.  If  the  taps  are  24  inches  long,  there 
should  be  a  depth  of  40  inches  of  oil.  If  the  articles 
are  longer,  the  tank  should  be  proportionally  deeper. 

A  precaution  that  should  always  be  observed  when 
hardening  large  pieces  of  work,  when  they  are  to 
be  quenched  in  a  bath  of  oil,  consists  in  protecting  the 
hands  and  arms  of  the  operator  to  prevent  burning 
from  the  fire,  which  results  when  a  piece  of  red-hot 
steel  is  immersed  in  oil.  This  is,  of  course,  simply  a 
burning  of  the  surface  oil  as  the  steel  passes  through 
it,  but  it  is  liable  to  flash  high  enough  to  bum  the 
hands  and  arms  unless  they  are  protected  in  some 
manner. 

When  hardening  long  articles,  it  is  found  much  more 
convenient  if  the  tanks  containing  the  cooling  liquid 
are  so  located  that  the  tops  of  the  tanks  are  nearly  on 
a  level  with  the  floor — say  12  or  15  inches  above  it. 

The  toolmaker  should,  when  making  adjustable 
taps,  reamers,  etc.,  of  the  description  shown  in  Fig.  128, 
leave  a  portion  on  the  end  solid,  as  shown  in  Fig.  129, 
to  prevent  the  tool  springing  out  of  shape.  The  hole 
for  the  adjusting  rod  should  be  filled  with  fire-clay, 
the  article  packed  with  the  mixture  of  charcoal  and 


How  to  harden  an  adjustable  reamer. 


charred  leather,  and  subjected  to  a  very  low  red  heat, 
and  dipped  in  raw  linseed  oil,  warmed  to  about  90 
degrees  Fahr.  The  length  of  time  it  should  be  sub- 
jected to  heat  after  it  is  red-hot  depends  on  the  size, 


§ 


Figure  129 

of  reamer. 


The  Derry  CoUard  Co. 

Solid  portion 


Figure  128.     An  adjustable  reamer. 

quality  of  steel  used,  and  the  work  it  is  to  do.  It 
will  vary  from  i  to  2^  hours.  The  temper  may  be 
drawn  to  a  light  straw  or  a  full  straw  color.  The 
shank,  and  ends  of  flutes  nearest  the  shank,  should  be 
drawn  to  a  blue.  When  drawing  the  temper,  the 
reamer  or  tap  may  be  placed 
in  a  kettle  of  oil  heated  to 
the  proper  degree  for  the 
cutting  edges.  The  shank 
may  be  drawn  lower  in  a 
flame,  or  heat  may  be  ap- 
plied at  the  shank  end  by 
means  of  a  flame  from  a  gas  jet,  Bunsen  burner,  or 
any  other  means,  allowing  the  heat  to  run  toward  the 
cutting  end.  After  the  reamer  has  been  hardened  and 
ground  to  size,  the  extreme  end  may  be  ground  off 
enough  to  allow  the  slots  to  extend  to  the  end. 

Dies  used  for  swaging  tubing  are  a  source  of  an- 
noyance when  hardened  by  methods  usually  employed, 
as  the  unequal  sizes  of  the  different  portions  cause 
them  to  spring  out  of  shape,  and  their  shape  is  such 
that  it  is  next  to  impossible  to  grind  them  in  a  manner 
that  insures  satisfaction  when  they  are  used. 

Pack  hardening  furnishes  a  method  whereby  this 

aa3 


Box  for  heating  swaging  dies. 

class  of  work  can  be  made  hard  enougli  to  do  the  work 
required  of  them,  and  they  do  not  alter  in  shape  enough 
to  require  grinding.  For  this  reason  the  extremely 
hard  surface,  which  comes  in  contact  with  the  contents 
of  the  bath,  need  not  be  removed  by  grinding. 

When  making  swaging  dies  of  the  description 
mentioned,  best  results  will  follow  if  they  are  made  of 
tool  steel  of  i^  to  I  }4^  per  cent,  carbon.  .  Block  to  shape, 
anneal  thoroughly,  and  finish  to  size.  When  harden- 
ing, the  dies  should  be  wired  and  packed  in  a  box, 
as  shown  in  Fig.  130,  placing  charred  leather  all 
around  the  die  for  a  distance  of  %  inch  to  i  inch.  The 
balance  of  the  box 
may  be  filled  with   ^^^  ^'^"'"^  ^3°- 

packing     mixture       ^8\i  Box  for  hardening 

that  has  previously        1   V*  swaging  dies.  ^v 

been    used.      Run 

for  about  4  hours 

after  they  have 

reached  a  medium 

red  heat.     It  is 

necessary  to    give 

articles  of  this  description  a  trifle   higher  heat  than 

if  hardening  cutting  tools  made  from  the  same  stock. 

As  hardness  is  the  required  quality,  the  dies  should 
be  left  as  hard  as  when  taken  from  the  bath,  which 
should  be  raw  linseed  oil  at  a  temperature  of  about  60 
degrees  Fahr. 

A  careful  study  of  the  pack  hardening  method 
will  help  every  one  handling  steel.  It  often  makes 
possible  the  use  of  lower  grade  steels,  and  it  enables 
pieces  to  be  made  of  any  desired  shape  with  the  knowl- 
edge  that  they  can  be  hardened  without  cracking. 


Tke  Derry  Collard  Co. 


224 


Case  Hardening, 


6--^=^  .^=^=^>© 


CO 

When  wrought  iron  or  machinery  steel — especially 
the  latter — will  answer  the  purpose  as  well  as  tool  steel, 
they  are  generally  used.  The  first  cost  is  less,  and  it 
can  be  machined  much  more  cheaply,  and  in  many  cases 
it  is  better  adapted  to  the  purpose. 

Machinery  steel  is  made  by  two  entirely  different 
processes,  namely:  the  Open  Hearth  and  the  Bessemer 
processes.  Each  method  produces  steel  adapted  to 
certain  classes  of  work.  There  are  many  grades  of 
steel  made  by  each  of  these  processes,  these  being  de- 
termined by  the  amount  of  carbon  or  other  elements 
present  in  the  steel.  Machinery  steel  is  not  only  valu- 
able to  the  manufacturer  on  account  of  its  low  first  cost, 
as  compared  with  tool  steel,  and  the  ease  with  which 
it  may  be  worked  to  shape,  but  it  possesses  the  quality 
of  toughness,  and  is  not  so  susceptible  to  crystalliza- 
tion from  the  action  of  shocks  and  blows.  A  very 
valuable  feature  is,  that  by  subjecting  it  to  certain 
processes,  the  surface  may  be  made  extremely  hard, 
while  the  interior  of  the  steel  will  be  in  its  normal 
condition,  thereby  enabling  it  to  resist  frictional  wear 
and  yet  possess  the  quality  of  toughness. 

The  hardening  of  surfaces  of  articles  made  of 
wrought  iron  and  machinery  steel  is  generally  termed 

225 


Case  hardening  a  few  pieces. 

**case  hardening,"  and  consists  in  first  converting  the 
surface  of  the  article  to  steel,  then  hardening  this  steel 
surface.  In  order  to  convert  the  surface  to  steel,  it  is 
necessary  to  heat  the  piece  red-hot,  then  treat  it  while 
hot  with  some  substance  which  furnishes  the  necessary- 
quality  to  cause  the  steel  to  harden  when  plunged  in  a 
cooling  bath. 

Most  machine  shops  have  some  means  whereby 
they  can  harden  screws,  nuts  and  similar  articles. 
Where  there  is  only  a  limited  .number  of  pieces  to 
harden,  it  is  customary  to  heat  the  work  in  a  black- 
smith's forge,  in  a  gas  jet,  or  in  any  place  where  a  red 
heat  can  be  given  the  piece.  When  hot,  sprinkle  with 
a  little  granulated  cyanide  of  potassium,  or  some  yel- 
low prussiate  of  potash,  or  a  mixture  of  prussiate  of 
potash,  sal  ammoniac  and  salt.  If  cyanide  of  potassium 
is  used,  it  is  advisable  to  procure  the  chemically  pure 
article,  as  much  better  results  may  be  obtained.  The 
reader  should  bear  in  mind  that  this  is  a  violent  poison. 
Re-heat  to  a  red  and  plunge  in  clear,  cold  water.  When 
there  are  large  quantities  of  work  to  harden,  this  is  an 
expensive  as  well  as  a  very  unsatisfactory  way.  To 
case  harden  properly,  one  must  understand  the  ma- 
terial of  which  the  article  is  made  and  the  purpose  for 
which  it  is  to  be  used — whether  it  is  simply  to  resist 
friction  or  wear,  or  to  resist  sharp  or  heavy  blows,  a 
bending  or  twisting  strain,  or  whether  it  is  merely  de- 
sired to  produce  certain  colors. 

We  will  first  consider  the  case  hardening  of  work 
that  simply  needs  a  hard  surface,  with  nothing  else  to 
be  taken  into  consideration.  Pack  the  articles  in  an 
iron  box  made  for  this  purpose,  as  shown  in  Fig.  131. 
The  size  and  shape  of  the  box  used  depend,  as  a  rule, 

226 


Case  hardening  in  a  gas  pipe. 

on  what  can  be  found  in  the  shop.  But  when  results 
are  to  be  taken  into  consideration,  it  is  advisable  to 
procure  boxes  adapted  to  the  pieces  to  be  hardened. 
It  is  not  policy  to  pack  a  number  of  small  pieces, 
which  do  not  require  a  deeply  hardened  portion,  in  a 
large  box,  especially  if  it  is  desirable  to  have  a  uni- 
formity in  the  hardened  product,  as  the  pieces  which 


Figure  131.      Box  for  case  hardening. 

are  near  the  walls  of  the  box  will  become  red-hot  long 
before  those  in  the  center.  And  as  steel  or  iron 
absorbs  carbon  only  when  red-hot,  the  pieces  nearest 
the  outside  would  be  hardened  to  a  greater  depth 
than  those  near  the  center  of  the  box. 

For  small  articles,  where  but  a  few  pieces  are  to 
be  hardened  at  a  time,  a  piece  of  gas-pipe  may  be  used. 
Screw  a  cap  solidly  on  one  end  or  plug  the  end  with  a 
piece  of  iron,  using  a  pin  to  hold  it  in  place.  The 
outer  end  may  be  closed  by  means  of  a  piece  made  in 
the  form  of  a  cap  to  go  over  the  end,  or  it  may  be  a 
loose-fitting  plug  held  in  place  by  a  pin,  as  shown  in 
Fig.  n8.  When  a  hardening  box  of  the  description 
shown  in  Fig.  131  is  used,  the  heat  may  be  gauged 
nicely  by  running  test  wires  through  the  cover  to 
bottom  of  tube,  as  shown  in  Fig.  126.  Pack  the  pieces 
of  work  in  a  mixture  of  equal  parts,  by  measure,  of 


az7 


How  to  pack  for  case  hardening. 

granulated  raw  bone  and  granulated  charcoal  mixed 
thoroughly  together.  Cover  the  bottom  of  the  harden- 
ing box  to  a  depth  oi  1%  inches  with  the  mixture, 
pack  a  row  of  work  on  this,  being  sure  that  the  arti- 
cles do  not  come  within  X  ^^  ^  i^^^  of  each  other, 
or  within  i  inch  of  the  walls  of  the  box.  Cover  this 
with  the  packing  material  to  a  depth  of  half  an  inch. 


Test  wire! 
Test  wire  I 


QL 


The  Deny  Collard  Co. 

Figure  132.     A  method  of  using  test  ynttz. 


Tamp  down,  put  on  another  layer,  and  so  continue 
until  the  box  is  filled  to  within  i  inch  of  the  top. 
Fill  the  remaining  space  with  refuse  packing  material 
left  over  from  previous  hardenings,  if  you  have  it. 
If  not,  fill  with  charcoal  or  packing  material,  tamp 
well,  put  on  the  cover,  and  lute  the  edges  with  fire- 
clay to  prevent  as  much  as  possible  the  escape  of  the 
gases.  This  is  necessary,  as  the  carbon  is  given  off 
from  the  packing  material  in  the  form  of  a  gas.  Then 
again,  if  there  are  any  openings,  the  direct  heat  will 
penetrate  these  and  act  on  the  work  in  a  manner  that 
gives  unsatisfactory  results. 

If  the  articles  are  so  large  that  they  would  not  cool 
below  a  red  heat  before  reaching  the  bottom  of  the  bath, 
they  should  be  wired,  as  shown  in  Fig.  130,  before  put- 

228 


Figure  133. 

Bath  for  case  hardening 

small  pieces. 


o     o 
000 


To  case  harden  many  small  pieces. 

ting  in  the  hardening  box.  Use  iron  binding  wire,  suf- 
ficiently strong  to  hold  the  piece  when  it  is  worked 
around  in  the  bath.  If  the  articles  are  too  heavy  for 
wiring,  we  must  devise  some  other  way  of  holding — 
either  tongs  or  grappling  hooks.  If  the  pieces  are 
small,  they  can  be  dumped  directly  from  the  box  into 
the  tank,  sifting  the  work  out  of  the  box  somewhat 
slowly,  so  that  the 
articles  will  not  go  <^ 
into  the  bath  in  a 
body.  If  the  tank 
is  large  enough,  it 
is  a  good  plan  to 
have  wires  across 
from  side  to  side, 
about  4  inches 
apart  in  horizontal 
rows.  Have  the 
rows  3  or  4  inches 
apart.  Do  not  put 
any  two  consecu- 
tive rows  of  the  wires  underneath  each  other,  but  in  such 
a  manner  that  the  work  will  strike  the  wires  as  it  passes 
to  the  bottom  of  the  tank.  In  striking  these  wires,  the 
work  will  be  separated,  and  any  packing  material  ad- 
hering to  it  will  be  loosened  by  the  jar.  The  work  will 
also  be  turned  over  and  over,  thus  presenting  all  sides 
to  the  cooling  effects  of  the  bath  as  it  passes  through. 
These  wires  can  be  arranged  as  shown  in  Fig.  133  by 
taking  two  pieces  of  sheet  metal,  a  little  shorter  than  the 
inside  length  of  the  tank,  drilling  holes  in  them  as  de- 
scribed in  the  arrangement  of  wires,  and  wires  can  be 
passed  through  these  holes  and  riveted,  thus  making  a 


.-"hS^ 


W<'<<yMMMWWi<!M    \M/WMWWM//W/<^ 


The  Derry  Collard  Co, 


229 


Details  of  tank  for  hardening  small  work. 

permanent  fixture  that  can  be  placed  in  the  tank  and 
taken  out  at  will.  The  distance  the  wires  are  apart  can 
be  varied  to  accommodate  the  particular  kind  of  work 
that  is  to  be  done.  They  must  be  far  enough  apart  so 
that  the  work  cannot  become  lodged  on  them. 

This  simple  device  does  away  with  the  liability  of 
soft  spots  in  pieces  of  work  that  are  case  hardened.  Do 
not  have  any  wires  within  8  or  lo  inches  of  the  bottom 
of  the  tank.  Have  a  coarse  screen  or  a  piece  of  sheet 
metal  drilled  full  of  holes  somewhat  smaller  than  the 
piece  we  are  to  harden.  Block  it  up  about  4  inches 
above  the  bottom,  to  allow  a  free  circulation  of  water 
underneath  it.  This  also  allows  the  water  to  pass 
through  it  around  the  work,  and  the  packing  material 
will  pass  through  it,  giving  the  water  a  better  chance 
to  get  at  the  work.  The  water  inlet  should  be  at  the 
bottom  of  the  tank,  and  we  should  have  an  outlet  about 
2  inches  from  the  top  to  allow  the  surface  water  to 
escape.  The  cold  water  coming  up  from  the  inlet  at 
the  bottom  should  be  turned  on  before  we  dump  the 
work,  allowing  it  to  run  until  the  work  is  cold.  In 
heating  the  work,  any  form  of  furnace  that  will  give 
the  required  heat  and  maintain  it  evenly  for  a  sufficient 
length  of  time  will  do. 

The  cover  of  the  boxes  should  have  several  %  inch 
holes  drilled  in  the  center,  as  shown  in  Fig.  26.  After 
putting  the  cover  in  place,  put  pieces  of  ^  inch  wire 
through  these  holes  down  to  the  bottom  of  the  boxes, 
allowing  them  to  stick  up  an  Inch  above  the  cover,  to 
enable  us  to  get  hold  of  them  with  the  tongs.  The 
boxes  may  now  be  put  in  the  fire,  and  subjected  to  a 
heat  which  should  vary  according  to  the  character  of 
the  work.     The  work  should  be  heated  to  a  red,  and 

230 


Unsatisfactory  to  gauge  heat  by  total  time. 

for  some  classes  of  work  it  may  even  be  brought  to  a 
bright  red.  When  it  is  thought  that  the  work  has  been 
in  the  fire  long  enough  to  heat  through,  draw  one  of 
the  wires  with  a  long  pair  of  tongs.  If  the  wire  is  red 
the  entire  length,  time  from  then.  If  not,  wait  a  few 
minutes  and  draw  another,  and  so  on  until  one  is  drawn 
that  is  red  the  entire  length. 

The  writer  considers  this  the  proper  method  to 
employ  in  timing  all  work  being  heated  in  the  fire, 
whether  it  is  to  be  annealed  or  case  hardened,  charging 
for  hardening  by  the  Harveyizing  method,  or  when  we 
are  pack  hardening  tool  steel.  If  the  work  is  timed 
from  the  time  it  is  put  in  the  fire,  the  results  will  be 
uncertain,  as  the  fire  is  hotter  one  day  than  it  is  another. 
Sometimes  the  fire  acts  dead,  another  day  lively,  so  the 
box  is  longer  in  heating  at  one  time  than  at  another; 
but  if  it  is  timed  from  the  period  when  the  work  com- 
mences to  take  carbon,  the  results  will  be  as  nearly- 
uniform  as  it  is  possible  to  get  them,  provided  the  heat 
is  uniform,  which  can  be  gauged  quite  closely  by  the 
eye.  Better  results  can  be  obtained  by  the  use  of  the 
pyrometer,  although  for  ordinary  work  this  is  not 
necessary.  After  running  the  work  the  proper  length 
of  time,  which  varies  according  to  the  nature  of  the 
steel  and  the  purpose  for  which  it  is  intended  (small 
articles,  %  inch  or  less,  which  do  not  require  anything 
but  a  hard  surface,  should  be  run  one  or  two  hours 
after  they  are  red-hot),  dump  into  the  water. 

If  it  is  desired  to  have  them  colored  somewhat, 
hold  the  box  about  a  foot  or  i8  inches  above  the  tank, 
allowing  them  to  pass  this  distance  through  the  air  be- 
fore striking  the  water.  If  we  are  hardening  small 
screws  having  slots  for  screw-drivers,  and  are  harden- 

231 


Advice  as  to  use  of  packing  material. 

ing  simply  to  keep  the  screw-driver  from  tearing  the 
slot,  we  can  use  expended  bone  as  packing  material — 
i.  e. ,  bone  that  has  been  used  once  before.  It  will  make 
the  work  hard  enough  for  all  practical  purposes,  yet 
not  hard  enough  to  break.  If  we  wish  to  harden  deeper, 
we  must  run  about  five  hours  after  the  work  is  red. 
By  running  sixteen  or  twenty  hours,  we  can  harden  to 
a  depth  of  y&  inch.  In  the  case  of  small  articles,  it  is 
best  to  use  a  bone  not  coarser  than  what  is  known  as 
No.  2  granulated  raw  bone.  When  we  are  to  run  for 
a  long  period  of  time  in  the  oven,  we  should  use  a 
coarser  grade. 

When  it  is  necessary  to  harden  very  deep,  it  is  ad- 
visable to  pack  the  work  with  coarse  bone,  letting  it  run 
from  15  to  20  hours  in  the  fire,  then  taking  out  and  re- 
packing with  fresh  material.  Work  that  is  allowed  to 
run  for  too  long  a  time  with  the  same  packing  material 
is  very  liable  to  be  not  only  insufficiently  carbonized, 
but  to  be  in  a  measure  decarbonized  and  highly  charged 
with  phosphorus,  which  is  very  injurious  to  the  ma- 
terial we  are  using.  The  charcoal  used  in  the  mixture 
should,  if  possible,  be  the  same  size  granules  as  the  bone. 
The  commercial  article  is  much  superior  to  anything 
we  can  pound  and  sift,  so  it  is  policy  to  buy  it.  The 
first  cost  may  seem  a  trifle  stiff,  but  if  account  is  taken 
of  the  time  it  takes  to  pound  and  sift  a  barrel  of  char- 
coal, it  will  be  found  the  cheaper  article. 

There  are  many  special  preparations  used  in  case 
hardening,  some  of  which  are  excellent  for  special 
work,  while  some  are  good  for  all  kinds  of  work. 
When  we  wish  to  harden  deep  in  a  short  space  of  time, 
it  is  advisable  to  use  bone  black  in  place  of  granulated 
raw  bone.     Bone  black,   or  animal  charcoal,  as  it  is 

232 


Mixture  for  use  on  color  work. 

commercially  called,  is  prepared  by  burning  bones  in  a 
special  furnace.  It  comes  in  tbe  form  of  a  powder.  It 
leaves  a  finer  grain  in  the  work  hardened,  and  it  will 
make  it  stronger  than  if  hardened  with  raw  bone. 
Another  form  of  bone  which  gives  excellent  results  is 
called  hydrocarbonated  bone,  a  form  of  bone  black 
treated  with  oil  so  that  it  gives  off  its  carbon  more 

readily  than 
bl  either  form 
mentioned  be- 
fore. It  is  not 
generally  used, 
but  for  nice 
work  it  is  very 
satisfactory. 

If  we  wish  to 
give  a  nice  color 
to  our  work,  it  is 
necessary  to 
first  polish  it 
and  be  sure  it  is 
clean  when 
packed  in  the 
hardening  box. 
Use  the  follow- 
ing  mixture 
when  packing: 


Figure  1 34.      Bath  having  an  air  inlet  with  water, 
for  obtaining  colors. 


10  parts  No.  i  granulated  raw  bone. 
2  parts  bone  black. 
I  part  granulated  charred  leather. 
Mix  thoroughly  before  using.     The  results  will  be 
much  more  gratifying,  if  a  pipe  which  is  connected  with 
an  air  pump  is  run  up  into  the  water  inlet  pipe,  as  shown 


a33 


How  to  cool  case  hardened  work. 

in  Fig.  134.  By  this  means  a  jet  of  air  is  forced  into  the 
water  at  the  bottom  of  the  tank  in  stich  a  manner  that 
it  will  be  distributed  through  the  whole  bath,  in  order 
that  each  piece  of  work  may  come  in  contact  with  it  as 
the  work  passes  through  the  water. 

When  articles  are  hardened  by  the  first  process 
mentioned,  heating  in  the  fire  and  treating  with  cyanide 
of  potassium,  very  nice  colors  can  be  obtained  by  taking 
a  piece  of  gas  pipe,  putting  one  end  in  the  bath  and 
blowing  through  it,  passing  the  work  through  the  air 
in  the  water  when  we  dip  it.  When  the  articles  are  thin, 
and  must  be  very  hard,  yet  tough,  it  is  best  to  use  a 
bath  of  raw  linseed  oil. 

If  this  bath  is  used,  it  is  advisable  to  attach  a  piece 
of  iron  binding  wire  to  each  piece  when  we  pack  the 
work,  allowing  the  wires  to  hang  over  the  sides  of  the 
box.  When  we  take  the  box  from  the  fire,  the  articles 
can  be  removed  from  it  and  immersed  in  the  oil  by 
means  of  the  wires.  They  should  be  worked  around 
well  in  the  bath  until  the  red  has  disappeared,  but  in 
such  a  manner  that  broad  sides  are  not  moved  against 
the  cool  oil,  or  the  articles  may  spring.  By  taking  this 
precaution,  there  will  be  no  difficulty  in  obtaining  satis- 
factory results  in  practically  all  cases. 

The  advent  of  the  bicycle  opened  the  eyes  of  me- 
chanics to  the  fact  that  a  low  grade  steel  could  be  used 
to  advantage  for  many  purposes,  where  formerly  it 
would  have  seemed  necessary  to  use  tool  steel  under 
similar  conditions. 

As  competition  made  it  necessary  to  produce  a 
machine  weighing  less  than  one  half  of  what  it  originally 
weighed,  and  capable  of  standing  up  under  greater 
strain,  methods  were  devised  whereby  low  grade  steel 

234 


Hardening  bicycle  parts. 

could  be  hardened  in  a  manner  that  insured  its  standing 
as  well  as  if  the  article  was  made  of  the  more  costly- 
tool  steel. 

Crank  axles  were  made  of  40-point  carbon  open 
hearth  steel,  which  was  given  sufficient  stiffness  by- 
heating  red-hot  and  plunging  in  hot  oil.  When  the 
percentage  of  carbon  was  lower  than  that  mentioned — 
40-point^it  was  sometimes  found  necessary-  to  pack 
the  axles  in  a  box  with  granulated  wood  charcoal,  sub- 
jecting them  to  a  red  heat  for  a  period  of  from  2  to  6 
hours;  they  were  then  dipped  in  hot  oil.  If  the  per- 
centage of  carbon  was  too  low  to  insure  hardening  by 
this  process,  they  were  packed  in  a  box  with  equal 
parts  of  charred  leather  and  charcoal,  run  for  a  suffi- 
cient length  of  time,  and  quenched  as  described. 

It  was  found  necessary  to  make  handle  bar  binders 
very  light.  When  made  of  tool  steel,  hardened  and 
tempered,  the  cost  was  too  great,  and  if  made  of  ordi- 
nary machine  steel,  case  hardened,  they  were  elastic, 
but  stretched  when  strain  was  put  on  them.  By  using 
a  30-point  carbon  steel  packing  in  charcoal,  and  running 
I  hour  after  they  were  red-hot,  then  plunged  in  hot  oil, 
they  gave  as  good  satisfaction  as  though  made  of  tool 
steel,  while  the  cost  of  machining  was  not  one-quarter 
as  much. 

Hardening  bevel  gears  for  bevel  gear  chainless 
bicycles  caused  a  great  many  anxious  moments  in  shops 
where  it  was  attempted.  One  prominent  manufactur- 
ing concern  lost  at  one  time  75  per  cent,  of  all  gears 
hardened,  according  to  their  own  statement. 

At  the  time  mentioned  the  writer  was  connected 
with  a  concern  manufacturing  a  high-grade  chainless 
wheel.     The  gears  were  of  the  design  represented  in 

ass 


Case  hardening  bicycle  parts. 

Fig"-  135-  They  were  made  of  40-point  carbon  open 
hearth  steel,  which  was  extremely  low  in  phosphorus. 
When  hardened,  they  were  packed  in  a  hardening  box 


Crank  Axle  Gear 


Pinion  Gear 


Figure  135. 

Bicycle  parts  case 

hardened. 


Cerry  ColUrd  Co, 


with  a  mixture  of  granulated  charred  leather  and  char- 
coal, run  at  a  red  heat  for  a  sufficient  length  of  time  to 
make  the  teeth  hard  enough  to  resist  wear,  yet  not 
brittle  enough  to  break  when  in  action.  This  was  the 
reason  it  was  necessary  to  use  a  steel  of  a  very  low 
percentage  of  phosphorus. 

The  crank  axle  gear,  as  shown  above,  was  run 
I  ^  hours  after  it  was  red-hot,  then  dipped  in  a  bath  of 
raw  linseed  oil  at  a  temperature  of  loo  degrees  Fahr. 

236 


DifFerent  case  hardening  results. 

The  surfaces  of  the  teeth  were  extremely  hard ;  the  gear, 
being  made  light  to  reduce  weight,  necessarily  had  to 
be  very  stiff,  yet  tough.  They  gave  the  best  of  satis- 
faction. Another  concern  in  the  same  line  of  business 
packed  their  gears  in  granulated  raw  bone,  with  the  re- 
sult they  were  so  brittle  it  was  found  impossible  to  use 
them.  Still  another  packed  their  gears  in  raw  bone,  run 
them  for  one  hour  after  they  were  red-hot,  then  allowed 
them  to  cool,  reheated  and  hardened.  The  gears  were  so 
brittle  the  teeth  would  break  when  the  surfaces  were 
not  sufficiently  hard  to  resist  wear.  Both  concerns 
adopted  the  method  in  use  in  our  factory  and  had 
excellent  results. 

While  bone  is  an  excellent  hardening  agent,  it  is 
not  good  practice  to  pack  steel  in  it  for  case  hardening, 
if  brittleness  is  objectionable  in  the  hardened  product, 
because,  as  previously  stated,  raw  bone  contains  phos- 
phorus, and  phosphorus  when  present  in  steel,  es- 
pecially in  combination  with  carbon,  causes  the  steel  to 
be  brittle. 

The  pinion  gear,  shown  in  Fig.  135  on  preceding 
page,  was  hardened  in  the  same  manner  as  the  one 
mentioned,  with  the  exception  of  the  temperature  of 
the  bath,  which  was  about  60  degrees.  When  hard- 
ening the  small  gears,  it  was  found  possible  to  wire 
several  on  the  same  wire,  being  careful  to  have  suffi- 
cient space  between  them  to  insure  good  results. 
The  advantage  of  this  method  of  wiring  was  that  a 
great  amount  of  time  was  saved  when  dipping  in  the 
bath.  While  it  was  necessary  to  dip  the  large  gear 
in  the  bath  in  a  vertical  position,  working  it  up  and 
down,  the  small  gears  were  dipped  in  any  position,  as 
their  shape  prevented  their  springing. 

237 


Case  hardening  small  screws. 

The  gears,  shown  in  Fig.  136,  were  used  on  the  rear 
end  of  the  gear  shaft  and  rear  hub,  and  were  hardened 
in  the  same  manner  as  the  crank  axle  gear. 


Th«  Derry  Collard  Co, 


Hub  Gear 


Geai  Shaft  Rear  End  Gear 

Figure  136.     Bicycle  parts 
case  hardened. 

While  the  critic  might 
claim  that  some  of  the  ex- 
amples given  do  not  prop- 
erly belong  under  the  head 
of  case  hardening,  it  has 
seemed  advisable  to  group 
them  under  this  head,  be- 
cause they  are,  as  a  rule,  so  classified  in  most  shops. 

It  is  generally  advisable  when  case  hardening 
screws  made  of  Bessemer  steel  wire,  to  pack  in  expended 
bone.  In  this  way  the  extreme  brittleness  incident  to 
the  use  of  raw  bone  is  done  away  with  in  a  great 
measure.  The  writer  has  seen  batches  of  small  screws 
(^  inch  and  under)  made  of  Bessemer  screw  stock, 
which  was  packed  in  raw  bone  and  hardened,  so  brittle 
that  they  would  break  from  the  necessary  power  ap- 
plied to  a  screw-driver  to  screw  them  into  the  hole.  At 
the  same  time,  when  annealed,  they  filed  easier,  and 
were  apparently  softer  than  a  piece  of  the  rod  they  were 
made  from.  They  had  been  heated  to  the  different 
temper  colors  in  order  to  toughen  them,  but  it  did  no 

*38 


Charred  leather  toughens. 

good.     They  were  so  brittle,  even  when  annealed,  that 

they  were  useless. 

Yet  screws  made  from  stock  out  of  the  same  batch, 

packed  in  expended  bone  and  run  for  the  same  length 

of  time,  were  apparently  all  right.     Had  charred  leather 

been  used,  it 
would  have  made 
them  tougher,  but 
the  expended  bone 
made  them  tough 
enough  for  all 
practical  purposes. 
As  it  is  much 
cheaper  and  more 
readily  obtained, 
it  is  generally  used 
for  work  of  this 
class. 

When  case  hard- 
ening small  pieces, 
which  do  not  re- 
quire a  deeply 
hardened  portion, 
but  which  must  be 
uniform,  as  bicycle 
chain  links,  it  is 
advisable  to  use 
boxes  made  espe- 
cially for  them,  in 
box  may  become 
The  writer  has  in 


Thu  Derry  CoUard  Co 


Fig.  137.      Another  form  of  box 
for  case  hardening. 


order   that    all    the   pieces   in   the 

heated  at  about  the  same  time. 

mind  a  certain  stock  used  for  making  bicycle  chain 

block  links,   which  was  packed  in  a  box   of  the   de- 


239 


How  to  pack  snap  gauges. 

scription  shown  in  Fig.  137,  using  as  packing 
mixture  equal  parts  animal  charcoal,  wood  char- 
coal and  charred  leather.  The  work  was  run  45 
minutes  after  it  became  red-hot,  then  dumped  in  cold 
water,  and  gave  excellent  results.  The  links  tested 
showed  up  well,  and  the  chains  gave  the  best  of  satis- 
faction when  on  the  wheels.  A  different  stock  was 
procured,  and  it  was  found  by  experiment  that  links 
made  from  the  new  stock  could  be  run  only  25  minutes 
after  they  became  red-hot.  If  run  the  same  length  of 
time  as  those  made  of  the  first  stock  used,  they  would 
break  very  easily,  but  when  run  only  25  minutes  gave 
very  good  satisfaction. 

In  many  shops  it  is  customary  to  make  snap  gauges 
of  machine  steel.  They  are  much  easier  made,  the 
cost  of  material  is  less,  and,  if  hardened  properly,  they 
will  wear  well.  It  is  best,  in  cases  of  this  kind,  to  use 
open  hearth  steel  rather  than  Bessemer,  as  the  latter 
runs  more  uneven.  The  best  results  will  be  obtained 
if  we  use  as  packing  material  granulated  leather  instead 
of  bone.  When  packing,  mix  with  an  equal  amount 
of  granulated  charcoal,  run  five  or  six  hours,  if  the 
gauge  is  %  inch  thick  or  more.  Run  at  a  very  low 
heat,  and  dip  in  the  oil  bath.  It  will  be  found  to  be 
very  hard,  and  probably  straight.  If  hardening  small 
pieces,  it  is  advisable  to  use  smaller  boxes  than  when 
large  pieces  are  being  treated,  as  it  takes  some  time  to 
heat  a  large  box  through.  Pieces  near  the  walls  of  the 
box  will  become  hot  quicker  than  those  in  the  center, 
and  consequently  will  be  hardened  deeper. 

Many  pieces  of  work  are  made  of  tool  steel  when 
machine  steel  would  answer  the  purpose  as  well,  or 
better,  were  it  not  for  the  coarseness  of  the  grain  when 

040 


Machine  steel  used  as  tool  steel. 

the  piece  is  case  hardened.  The  fine  grain  may  be 
necessary  to  resist  pressure  and  wear  on  some  small 
part  of  the  surface,  or  possibly  it  is  to  be  subjected  to 
the  action  of  blows,  and  the  grain  being  coarse,  the 
surface  has  no  backing  and  is  soon  crushed  in.  The 
causes  of  the  open  grain  are :  first,  that  it  is  the  natural 
condition  of  the  stock ;  second,  the  pores  are  open  when 
heated,  and  the  steel  is  absorbing  carbon.  The  higher 
the  heat  to  which  the  pieces  are  subjected,  the  coarser 
the  grain. 

It  is  possible  to  heat  machine  steel  in  such  a  man- 
ner as  to  produce  a  fine  grain — in  fact,  as  fine  as  that 
of  the  nicest  tool  steel.  While  the  writer  would  not  be 
understood  as  advocating  the  use  of  machinery  steel  in 
the  making  of  nice  tools,  as  so  good  an  article  cannot 
be  produced  as  if  made  of  tool  steel,  yet  for  certain 
purposes  cutting  tools  are  made  of  a  good  grade  of  open 
hearth  steel,  case  hardened  very  deep,  with  fine  compact 
grain,  which  gives  excellent  results.  This  is  particu- 
larly the  case  where  the  cutting  part  is  stubby  and 
strong.  Cams  made  of  low  grade  steel,  and  hardened 
by  this  method,  will  resist  wear  as  well  as  though  made 
of  tool  steel  and  hardened,  and  they  are  not  as  liable  to 
flake  off  or  break.  Punch  press  dies  that  are  to  be  used 
for  light  work,  cutting  soft  metals  where  there  are  no 
projections,  will  do  very  satisfactory  work.  Gauges, 
whether  they  be  snap,  plug,  ring  or  receiving,  are 
hardened  with  much  less  liability  of  their  going  out  of 
shape,  are  easier  to  make,  and  will  wear  as  long  as 
though  made  of  tool  steel.  Then,  too,  the  necessity  of 
allowing  them  to  ''age"  after  hardening,  before  grind- 
ing to  size,  as  is  the  case  when  gauges  are  made  of  tool 
steel  for  accurate  work,  is  done  away  with. 

Z41 


What  is  needed  in  case  hardening. 

Many  bicycle  parts,  formerly  made  of  a  good  grade 
of  tool  steel,  are  now  made  of  machine  steel,  and  the 
best  of  results  are  obtained.  Such  is  not  apt  to  be  the 
case  if  they  are  simply  case  hardened  by  the  ordinary 
method,  as  the  grain  is  too  coarse  to  resist  the  peculiar 
action  of  the  balls,  particularly  on  the  cones  and  ball 
seats.  Spindles  of  machines,  where  there  is  considera- 
ble tendency  to  wear,  also  a  pounding  or  twisting  mo- 
tion to  resist,  where  tool  steel  would  be  liable  to  break 
and  ordinary  case  hardening  would  yield  to  such  an 
extent  as  to  make  the  bearings  out  of  round,  can  be 
treated  very  successfully  by  this  method. 

All  that  is  needed  is  a  good  hardening  furnace, 
large  enough  to  receive  as  many  boxes  as  we  may  need, 
a  plentiful  supply  of  boxes,  some  granulated  raw  bone, 
a  good  supply  of  charcoal  and  a  small  amount  of  hydro- 
carbonated  bone,  and  some  charred  leather  for  our 
nicest  work.  We  should  also  have  a  suitable  supply  of 
water  in  a  large  tank,  and  a  smaller  tank  arranged  so 
that  we  can  heat  it  to  any  desired  temperature,  and  a 
bath  containing  raw  linseed  oil.  The  work  should  be 
packed  in  the  hardening  boxes  as  for  ordinary  case 
hardening,  run  about  the  same  length  of  time,  and  left 
in  the  oven  to  cool  the  same  as  for  annealing. 

When  cool,  the  articles  may  be  heated  in  the 
open  fire,  muffle  furnace  or  in  the  lead  crucible,  and 
hardened  the  same  as  tool  steel ;  or,  if  the  articles  are 
small,  and  there  are  many  of  them,  they  can  be  re- 
packed in  the  hardening  box  with  charcoal.  But  do 
not  use  any  carbonizing  substance,  as  that  would  have 
a  tendency  to  open  the  grain,  and  the  object  of  the 
second  heat  is  to  close  the  grain.  The  lower  the  hard- 
ening heat,  the  more  compact  the  grain  will  be,  as  is 

242 


Case  hardening  metal  cutting  tools. 

the  case  with  tool  steel.  This  method  not  only  gives  a 
close  grain,  but  a  very  strong,  tough  surface,  and,  the 
center  being  soft,  the  piece  is  very  strong. 

When  hardening  tools  whose  office  it  is  to  cut 
metals,  it  is  always  best  to  use  a  packing  mixture  of 
equal  parts  of  charred  leather  and  charcoal.  The 
kernels  should  be  fine  and  of  about  the  same  size,  if 
possible,  for  if  the  kernels  of  the  leather  were  large, 
and  those  of  the  charcoal  were  small,  the  tendency 
would  be  for  the  finer  to  sift  to  the  bottom  of  the  box. 
Leather  gives  a  stronger,  tougher  effect  than  bone,  it 
being  practically  free  from  phosphorus,  while  bone 
contains  a  large  percentage.  The  presence  of  phos- 
phorus in  steel  makes  it  brittle,  especially  when  com- 
bined with  carbon.  Yet  for  most  purposes  where  there 
are  no  cutting  edges  bone  works  very  satisfactorily  in 
connection  with  machinery  steel,  and  is  much  cheaper 
than  leather.  When  using  either  bone  or  leather,  mix 
with  an  equal  quantity  (by  measure)  of  granulated 
charcoal.  Being  well'  mixed,  the  particles  of  charcoal 
keep  the  kernels  of  bone  or  leather  from  adhering  to 
each  other  and  forming  a  solid  mass  when  heated. 
Then  again,  the  charcoal  has  a  tendency  to  convey  the 
heat  through  the  box  much  more  quickly  than  would 
be  the  case  were  it  not  used. 

If  small  pieces  are  to  be  hardened  that  do  not  need 
carbonizing  more  than  -^  of  an  inch  deep,  it  is  best  to 
use  No.  2  granulated  raw  bone.  If  the  pieces  require 
a  very  deep  hardened  section,  it  will  need  a  coarser 
grade,  as  they  must  run  longer  in  the  fire.  When 
hardening  bicycle  cones  and  similar  articles,  where  it  is 
necessary  to  carbonize  quite  deeply,  it  is  best  to  pack 
with  No.  3  bone  and  charcoal,  equal  parts,  or  better 

»43 


To  case  harden  thin  pieces. 

yet,  with  two  parts  raw  bone,  two  parts  charcoal  and 
one  part  bone  black  or  animal  charcoal.  Pack  in  the 
hardening  box,  as  previously  described,  run  in  the  fur- 
nace lo  hours  after  the  box  is  heated  through,  using 
the  test  wires  to  determine  the  beginning  of  the  heat. 
After  the  work  is  cold,  it  can  be  reheated  as  described 
and  hardened.  It  is  advisable  to  occasionally  break  a 
piece  of  work  and  examine  the  grain,  noticing  how 
deep  the  hardening  has  penetrated.    If  not  deep  enough, 


The  Derry  Collard  Co. 
Figure  138.      Piece  to  be  hardened,  leaving  the  center  soft. 

repack  in  the  boxes  with  fresh  material,  and  run  again ; 
but  if  directions  given  are  followed  closely,  results  will 
in  all  probability  be  found  satisfactory.  The  grain,  as 
far  in  as  the  carbon  has  penetrated,  should  be  as  fine 
as  that  of  hardened  tool  steel. 

In  hardening  thin  pieces,  where  it  is  necessary  to 
resist  wear  or  blows,  it  is  advisable  to  use  leather  as  a 
packing  material,  hardening  in  a  bath  of  raw  linseed 
oil.  The  pieces  will  be  found  extremely  tough  and 
hard.  It  is  sometimes  desirable  to  harden  the  ends  of 
a  piece  of  work,  leaving  the  center  soft.  Take,  for  in- 
stance, the  piece  shown  in  Fig.  138.     The  surface  of  the 


»44 


Case  hardening  thin  pieces. 


ends  marked  a  needs  hardening,  while  the  portions 
marked  b  should  be  soft.  Pack  the  ends  inside  and  out 
with  hydrocarbonated  bone  and  charcoal,  having  pre- 
viously filled  the  center  with  expended  bone.  Cover 
the  outside  of  the  center  with  expended  bone,  run  in 
the  oven  7  or  8  hours  after  the  box  is 
heated  through.  Allow  the  work  to 
cool  as  described,  remove  the  pieces 
from  the  box,  heat  the  ends  separately 
in  the  lead  cruci- 

Figure  139. 

How  to  dip  thin 

pieces. 


ble,  dip  in  a  bath 
of  lukewarm 
water,  dipping 
with   the   heated 


end 


up,     as 


shown  in  Fig.  139. 
Otherwise  the 
steam  generated 
from  contact  of 
the  hot  steel  with 
water  would  pre- 
vent the  water 
from  entering 
the  end  where  it 
dipped  with  the 
heated  end  down. 
If  the  water  can- 
not  enter  the 
work  and  get  at  the  portions  necessary  to  be  hard, 
they  certainly  will  not  harden.  If  the  piece  is  dipped 
with  the  heated  end  as  described,  the  water  readily 
enters.  The  ends  will  be  found  extremely  hard,  and 
the  grain  will  be  very  compact.     Not  only  is  this  so, 


The  Derry  GoUard  Co. 


Case  hardening  bicycle  axles. 

but  the  piece  will  be  much  less  liable  to  crack  than 
if  the  extreme  ends  were  dipped  first  and  hardened,  as 
would  be  the  case  with  the  heated  end  down. 


Tke  Dairy  Collard  Ck>. 


Figure  140.      Bicycle  axle. 


Another  method  employed  when  hardening  the 
ends  of  a  piece  of  work  and  leaving  the  center  soft,  can 
be  illustrated  by  the  bicycle  axle  shown  in  Fig.  140. 
The  ends  are  machined  to  shape,  the  center  being  left 
large,  as  represented  at  a.  The  axle  is  packed  in  the 
hardening  box  and  charged  with  carbon,  as  described. 
The  center  is  then  cut  below  the  depth  of  charging 
shown  at  d.  The  piece  is  ready  for  hardening.  This 
can  be  accomplished  by  heating  in  an  open  fire,  muffle 
furnace  or  lead  crucible,  and  dipping  in  the  bath. 

When  it  is  necessary  to  harden  the  center  of  a 
piece  and  leave  the  ends  soft,  it  can  easily  be  accom- 
plished.    If  the  ends  are  to  be  smaller  than  the  center, 

246 


How  to  harden  bicycle  chain  studs. 

the  pieces  may  be  packed  in  the  hardening  box  with 
raw  bone  and  charcoal.  Run  for  a  sufficient  length  of 
time  to  carbonize  to  the  desired  depth  of  hardening. 
Allow  the  pieces  to  cool  off.  When  cool,  machine  the 
ends,  as  shown  by  lower  cut  in  Fig.  141,  the  upper  cut 


The  Derry  Collard  Co. 

Figure  141.      Method  of  treatment  for  chain  studs. 

representing  the  piece  of  work  before  charging  with 
carbon;  the  lower,  after  machining  the  carbonized 
portions  at  the  ends.  It  may  now  be  heated  red-hot 
and  dipped  in  the  hardening  bath  in  the  usual  man- 
ner.    The  center  will  be  found  hard. 

A  method  employed  in  making  bicycle  chain  studs 
that  are  hard  in  the  center  at  the  point  of  contact  with 
the  block  link  and  soft  on  the  ends,  in  order  that  they 
may  be  readily  riveted  in  the  side  links,  consists  in 
taking  screw  wire  or  special  stud  wire  of  the  desired 
size,  packing  it  in  long  boxes  with  raw  bone  and  char- 
coal and  running  3  or  4  hours  after  it  is  red-hot.  Then 
allow  it  to  cool  off.  The  stock  is  now  placed  in  the 
screw  machine  and  cut  to  shape — that  is,  the  ends  are 
cut  down  to  proper  size.  The  center,  being  of  the 
proper  size,  is  not  machined.     The  studs  may  be  heated 

H7 


An  interesting  experiment. 

in  a  tube  in  any  form  of  fire  and  dumped  in  a  bath  of 
water  or  brine.  The  center  will  be  hard  enough  to  re- 
sist wear,  while  the  ends  will  be  soft,  the  carbonized 
portion  having  been  removed. 

An  interesting  experiment  can  be  tried,  which  in 
itself  is  of  no  particular  value,  except  that  it  acquaints 


a  &  a  b  a  b  q 


The  Derry  Collard  Co. 

Figure  142.      An  interesting  experiment. 

one  with  the  manner  in  which  carbon  is  absorbed  by- 
steel.  Take  a  piece  of  open  hearth  machinery  steel, 
turn  it  in  the  lathe  to  the  shape  shown  in  Fig.  142,  neck- 
ing in  every  half  inch  to  the  depth  of  }i  inch,  leaving 
the  intervening  spaces  }4  inch  long.  Pack  the  piece 
in  the  hardening  box  with  raw  bone  and  charcoal. 
Run  five  or  six  hours  after  the  box  is  heated  through. 
AVhen  cold,  turn  the  shoulders  marked  d  to  the  size  of 
a,  leaving  a  the  same  size  as  before  charging.  Heat  to 
a  low  red  and  dip  in  the  bath.  The  portions  marked 
a  will  be  found  hard,  while  the  balance  of  the  piece 
will  be  soft. 

When  pieces  are  to  be  case  hardened,  and  it  is  con- 
sidered desirable  to  leave  a  certain  portion  soft,  it  is 
accomplished  many  times  by  making  tongs  of  the 
proper  form  to  effectually  prevent  the  contents  of  the 
hardening  bath  coming  in  contact  with  the  portion  men- 

248 


Case  hardening  to  leave  soft  places. 


tioned      Suppose,  for  example,  a  piece  of  the  design 
shown  in  Fig.  143  is  to  be  case  hardened,  and  itisde- 


< PORTION-G^StRtD-SOFl 


The  Derry  Collard  Co. 

Figure  143.      Piece  with  portion  desired  soft. 

sired  to  leave  the  central  portion  marked  soft.     Make  a 
pair  of  tongs  to  grasp  the  piece,  as  shown  in  Fig.  144. 


It  will  be  seen  that 
tioned  is  eff  ect- 
the  tongs.  The 
in  the  bath,  and 
until  the  red  has 
it  may  be  dropped 
tank  and  left  until 
desirable  to  leave  a 


the  portion  men- 
ually  protected  by 
piece  may  be  dipped 
worked  around  well 
disappeared,  when 
to  the  bottom  of  the 
cold.  When  it  is 
portion  of  an  article 


i 


^ 


P 


Tba  Dtfiry  Collard  Co, 

Figure  144.     Tongs  for  handling  piece  shown  above. 

soft,  as  shown  in  Fig.  145,  it  is  sometimes  accomplish- 
ed by  covering  the  portion  to  be  soft  with  fire-clay,  as 
shown  in  lower  view.  The  fire-clay  may  be  held  in 
place  by  means  of  iron  binding  wire ;  sometimes  the 
fire-clay  is  held  in  place  by  means  of  plasterers'  hair, 


249 


The  use  of  fire-clay  for  soft  places. 

whicli  is  worked  into  the  mass  when  it  is  mixed  with 
water.  The  fire-clay  prevents  the  carbon  coming  in 
contact  with  the  stock  where  it  is  desired  soft. 


The  Derry  Collard  Co, 

Figure  145.     The  use  of  fire-clay  for  soft  spots. 


A  method  employed  in  some  shops  consists  in 
wrapping  a  piece  of  sheet  iron  around  the  article  over 
the  portion  de- 
sired soft,  as 
shown  in  Fig.  146. 
The  sheet  metal  is 
held  in  place  by 
means  of  iron 
binding  wire,  as 
shown. 


The  Derry  Oollard  Co. 


Figure  146.     Using  sheet  iron  to 
prevent  hardening. 


A  very  common  method,  which   is  costly  when 
many  pieces  are  to  be  treated,   consists  in  forcing  a 


250 


The  use  of  a  collar  in  case  hardening. 

collar  on  to  the  piece  over  the  portion  desired  soft,  as 
shown  in  Fig.  147.  The  collar  is  removed  alter  the 
article  is  hardened. 


Piece  to  be  hardened 


Collar 


The  Derry  Collard  Co. 


Collar  In  position 
Figure  147.      A  collar  for  keeping  portions  soft. 


When  machine  nuts  are  to  be  case  hardened,  and 
for  any  reason  it  is  desirable  to  have  the  interior 
threaded  portion  soft,  it  is  accomplished  by  screwing 
a  threaded  piece  of  stock  in  the  hole  before  the  nuts 
are  packed  in  the  hardening  box. 

As  carbon  can  not  penetrate  a  nickeled  surface, 
articles  are  sometimes  nickel-plated  at  portions  desired 
soft;  this,  however,  is,  generally  speaking,  a  costly 
method  of  accomplishing  the  desired  result. 

It  is  sometimes  considered  necessary  to  harden  the 


251 


Mow  to  produce  toughness. 

Surfaces  of  pieces  quite  hard  and  leave  the  balance  of 
the  stock  stiffer  than  would  be  the  case  where  ordinary- 
machinery  steel  is  used.  In  such  cases  many  times  an 
open  hearth  steel  is  selected,  which  contains  suf- 
ficient carbon,  so  that  it  will  become  very  stiff  when 
quenched  in  oil.  The  writer  has  in  mind  a  gun  frame 
which,  on  account  of  the  usage  to  which  it  was  to  be 
put,  must  have  a  hard  surface,  while  the  frame  itself 
must  be  very  stiff.  They  were  packed  in  a  mixture  of 
charred  leather  and  charcoal,  placed  in  the  furnace  and 
run  for  a  period  of  ij4  hours  after  they  were  red-hot. 
They  were  then  quenched  in  a  bath  of  sperm  oil.  The 
stock  used  was  30 -point  carbon  open  hearth  steel.  Were 
the  articles  heavier  or  a  greater  degree  of  stiffness  de- 
sirable, a  steel  could  be  procured  having  a  greater  per- 
centage of  carbon. 

When  toughness  or  strength  is  wanted  in  the  case 
hardened  product,  a  steel  having  much  phosphorus 
should  not  be  used ;  in  fact,  the  percentage  of  phosphorus 
should  be  the  lowest  possible,  as  steel  containing  phos- 
phorus, in  connection  with  carbon,  is  extremely  brittle. 
For  this  reason,  articles  which  must  be  extremely  tough 
should  not  be  packed  in  raw  bone,  as  this  contains  a 
very  high  percentage  of  phosphorus. 

At  times  a  job  will  be  brought  around  to  be  case 
hardened,  and  one  particular  part  will  be  wanted  quite 
hard,  while  the  balance  of  the  piece  will  not  require 
hardening  very  hard  or  deep.  In  such  cases,  if  the  por- 
tion mentioned  be  a  depression,  it  may  be  placed  upper- 
most in  the  hardening  box,  and  some  prussiate  of 
potash  or  a  small  amount  of  cyanide  of  potash  placed 
at  this  point,  the  piece  being  packed  in  granulated  raw 
bone  or  leather,  and  run  in  the  furnace  a  short  time. 


Furnaces  for  case  hardening. 

The  article  may  be  quenched  in  the  usual  manner.     The 
portion  where  the  potash  was  placed  will  be  extra  hard. 


The  'Deny  CoU«rd  Co, 
Figure  148.     Gas  furnace  for  case  hardening. 


The  furnace  used  in  case  hardening  should  receive 
more  consideration  than  is  many  times  the  case;  an 
even  heat  that  can  be  maintained  for  a  considerable 
length  of  time  is  essential  if  desi  results  are  desired. 

A  very  satisfactory  form  of  furnace  is  represented 
in  Fig.  148;   it  bums  illuminating  gas  as  fuel. 

When  it  is  considered  desirable  to  use  hard  coal  as 

aS3 


A  "home-made"  case  hardening  furnace. 

fuel,  the  furnace  made  by  the  Brown  &  Sharpe  Co. ,  of 
Providence,  R.  I.,  gives  excellent  results. 

When  it  is  considered  advisable  to  construct  on  the 


Figure  149.      ** Home-made"  fiiinace 
for  case  hardening. 


premises  a  furnace  burning  charcoal  or  coke,  the  form 
shown  in  Fig.  149  will  be  found  very  satisfactory. 

However,  the  form  and  size  of  furnace  depend  in  a 
great  measure  on  the  character  and  amount  of  work  to 
be  hardened. 

Baths   for   Case   Hardening. 

The  bath  that  is  to  be  used  for  cooling  work  being 
case  hardened  must  be  suitable  to  the  work  being 


254 


Various  styles  of  case  hardening  baths. 

hardened.  Where  work  is  case  hardened  in  large 
quantities,  it  is  customary  in  most  shops  to  harden  in 
iron  boxes.  When  the  work  is  in  the  proper  condition, 
the  box  is  inverted  over  a  tank  of  water  or  some  fluid, 
and  the  contents  dumped  into  the  bath.  If  the  pieces 
of  work  are  large  or  bulky,  and  the  tank  is  shallow, 
they  reach  the  bottom  while  red-hot,  and,  as  a  con- 
sequence, the  side  of  the  piece  that  lays  on  the  bottom 
will  be  soft.  In  order  to  overcome  this  trouble,  the 
tank  must  be  made  deep  enough  so  that  the  pieces  will 
be  sufficiently  chilled  before  reaching  the  bottom.  If 
it  is  not  considered  advisable  to  have  an  extremely  deep 
tank  and  the  pieces  are  large,  various  ways  are  taken 
to  insure  their  hardening. 

One  method  which  the  writer  has  used  with  excel- 
lent results  is  to  have  a  series  of  rows  of  wire  rods 
reaching  across  the  tank,  no  two  consecutive  rows  being 
in  the  same  vertical  plane,  as  mentioned  in  the  previous 
section.  The  work  as  it  descends  into  the  bath  strikes 
these  wires,  which  turns  them  over  and  over,  bringing 
all  portions  in  contact  with  the  contents  of  the  bath. 
These  wires  also  separate  the  pieces  from  each  other 
and  from  any  packing  material  which  may  have  a 
tendency  to  stick  to  them.  The  wires  also  retard  the 
progress  of  the  articles,  giving  them  more  time  to  cool 
before  reaching  the  bottom  of  the  bath. 

In  order  to  insure  good  results,  it  is  necessary  to 
have  a  jet  of  water  coming  up  from  the  bottom  of  the 
tank.  An  outlet  is  provided  near  the  top  for  an  over- 
flow. The  overflow  pipe,  of  course,  should  be  larger 
than  the  inlet  pipe,  and  should  be  located  far  enough 
below  the  top  edge  of  the  tank,  so  that  the  contents  will 
not  overflow  when  a  box  of  work  is  dumped  into  it. 


Bath  with  catch  pan, 


I 


Perforated  Catch  Pan 


W//f^//^/y'^/^/^/////^////^///^/M^/7/?///. 


In  order  to  get  tlie  hardened  pieces  out  of  the  bath 
easily,  it  is  necessary  to  provide  a  catch  pan,  as  shown 
in  Fig.  150.  The  bottom  of  this  pan  should  be  made  of 
strong  wire  netting  or  a  piece  of  perforated  sheet  metal, 
preferably  the  former.  The  holes  in  the  pan  allow  the 
packing  material  to  fall  through  to  the  bottom  of  the 

tank,  and  also 
allow  the  water 
from  the  supply 
pipe  to  circulate 
freely  around  the 
work  and  to  the 
top  of  the  bath. 
This  catch  pan 
should  be  provided 
with  strong  wire 
handles,  as  shown, 
in  order  that  it  may 
be  readily  raised. 

I  was  at  one  time 
requested  to  call  at 
a  shop  where  they 
were  having  very 
unsatisfactory  re- 
sults with  their 
case  hardening.  An  examination  showed  they  were 
dumping  their  product  into  a  barrel  of  water  to  harden. 
The  box  containing  the  work  was  inverted  over  this 
barrel,  and  the  work  and  packing  material  went  into 
the  water  in  a  lump.  Some  of  the  pieces  that  hap- 
pened to  get  out  of  this  mess  were  cooled  sufficiently 
to  harden  somewhat,  but  the  majority  of  the  pieces  were 
soft,  or  else  they  were  hard  on  one  side  and  soft  on  the 

256 


=s^ 


Tha  Dtsrry  Col  lard  Co. 

Figure  150.      Case  hardening  bath  with  catch 
pan  and  steam  pipe. 


How  a  temporary  bath  was  arranged. 

other.  An  examination  of  the  bottom  of  the  barrel 
showed  it  to  be  considerably  charred.  In  places  the 
outline  of  the  pieces  was  plainly  visible.  These  pieces 
had  reached  the  bottom  red-hot,  and  had  burned  their 
way  into  the  wood.  It  is  needless  to  say  that  the  side 
of  the  piece  of  work  which  was  down  did  not  harden. 

As  those  in  charge  of  the  work  did  not  think  it  ad- 
visable, considering  the  limited  amount  which  they  had 
to  case  harden,  to  get  a  tank  of  the  description  shown 
in  Fig.  150,  we  made  a  catch  pan  as  described,  blocked 
it  up  about  6  inches  from  the  bottom  of  the  barrel 
by  means  of  bricks.  We  then  bored  a  hole  into  the 
bottom  of  the  barrel,  screwed  in  a  piece  of  pipe,  and  by 
this  means  were  able  to  connect  an  ordinary  garden 
hose,  so  as  to  get  a  jet  of  water  coming  up  from  the 
bottom.  As  the  barrel  was  out  of  doors,  we  simply 
bored  a  two -inch  hole  about  two  inches  from  the  top  of 
the  barrel  for  an  overflow,  and  let  the  water  run  on 
the  ground.  When  the  work  was  ready  to  dump,  we 
sifted  it  out  of  the  box  into  the  water  gradually,  rather 
than  to  dump  it  in  a  body.  As  soon  as  the  box  was 
emptied,  we  grasped  the  wire  connected  with  the  catch 
pan,  and  raised  and  lowered  the  pan  in  a  violent  man- 
ner, in  order  to  separate  any  pieces  that  might  have 
lodged  together.  The  result  was  very  satisfactory,  and 
I  think  they  are  still  using  that  barrel. 

Baths  are  made,  when  large  quantities  of  work  are 
hardened,  with  some  means  of  keeping  the  work  in 
motion  after  it  reaches  the  bottom  of  the  bath.  This 
is  sometimes  done  by  mechanically  raising  and  lower- 
ing the  catch  pan,  and  at  the  same  time  turning  it 
around.  Then  again,  it  is  done  by  means  of  several 
sweeps,  which  are  attached  to  the  lower  end  of  a  verti- 

257 


Baths  with  air  pumps  or  perforated  pipes. 


cal  shaft,  the  shaft  resting  in  a  bearing  in  the  center  of 
the  catch  pan.  These  sweeps,  or  arms,  revolving,  keep 
the  pieces  in  motion,  turning  them  constantly,  but  un- 
less arranged 
properly,  they 
have  a  tendency 
to  gather  the 
work  in  batches, 
thereby  acting 
exactly  opposite 
from  what  they 
are  intended  to 
do.  Then  again, 
they  have  a  ten- 
dency to  scratch 
the  surface  of  the 
work,  which  is  a 
serious  objec- 
tion, if  color 


Supply  Pipe 

Figure  151. 


Bath  for  cooling  slender 
case  hardened  articles. 


work  is  wanted. 
When  it  is  de- 
sirable to  get  nice  colors  on  case  hardened  work,  an 
air  pump  may  be  connected  with  the  bath,  as  shown  in 
Fig.  134,  the  water  and  air  entering  the  bath  together. 
While  it  is  not  advisable  to  let  air  come  in  contact  with 
the  pieces  to  be  hardened  for  colors  while  passing  from 
the  box  to  the  water,  yet  the  presence  of  air  in  the 
water  would  have  the  effect  of  coloring  the  work  nicely. 
When  hardening  long  slender  articles  or  those 
liable  to  give  trouble  if  a  bath  of  the  ordinary  descrip- 
tion is  used,  excellent  results  may  be  obtained  by  the 
use  of  a  bath  with  perforated  pipes  extending  up  the 
sides  of  the  tank,  as  shown  in  Fig.  151. 

258 


Spring   Tempering, 


G^<^  .^=^n9 


CO 


When  it  is  necessary  to  give  articles  made  of  steel  a 
sufficient  degree  of  toughness,  in  order  that  when  bent 
they  will  return  to  their  original  shape,  it  is  accom- 
plished by  a  method  known  as  spring  tempering. 

The  piece  is  first  hardened,  then  the  brittleness  is 
reduced  by  tempering  until  the  article,  when  sprung, 
will  return  to  its  original  shape. 

Generally  speaking,  it  is  not  advisable  to  quench 
pieces  that  are  to  be  spring  tempered  in  cold  water,  as 
it  would  not  be  possible  to  reduce  the  brittleness  suffi- 
ciently to  allow  the  piece  to  spring  the  desired  amount 
without  drawing  the  temper  so  much  that  the  piece 
would  set.  Steel  heated  red-hot  and  plunged  in  oil  is 
much  tougher  than  if  plunged  in  water ;  and  as  tough- 
ness is  the  desired  quality  in  springs,  it  is  advisable  to 
harden  in  oil  whenever  this  will  give  the  required  result. 

For  many  purposes  a  grade  of  steel  made  especially 
for  springs  gives  better  results  than  tool  steel ;  for  in- 
stance, bicycle  cranks  made  of  a  40-point  carbon  open 
hearth  steel  will  temper  in  a  manner  that  allows  them 
to  stand  more  strain  than  if  made  of  the  finest  tool 
steel,  and  the  stock  does  not  cost  more  than  one-quarter 
the  price  of  tool  steel. 

When  springs  are  to  be  made  for  a  certain  purpose, 
259 


How  to  harden  clock  springs. 

it  is  generally  safer  to  state  the  requirements  of  the 
spring  to  some  reliable  steel  maker,  allowing  him  to 
furnish  the  stock  best  suited  for  the  purpose,  than  to 
attempt  to  specify  the  exact  quality  wanted — unless,  of 
course,  the  operator  or  manufacturer  has,  either  by  ex- 
perience or  by  study,  acquired  the  knowledge  necessary 
to  qualify  him  to  judge  as  to  the  quality  needed. 

As  previously  stated,  the  hotter  a  piece  of  steel  is 
heated  for  hardening  the  more  open  the  grain  becomes ; 
and  as  hardened  steel  is  strongest  when  hardened  at 
the  refining  heat,  it  is  always  advisable  to  heat  no  hot- 
ter than  is  necessary  to  accomplish  the  desired  result. 
But  as  springs  are  generally  made  of  a  steel  lower  in 
carbon  than  ordinary  tool  steel,  and  as  low  carbon 
steel  requires  a  higher  heat  to  harden  than  is  the  case 
when  tool  steel  is  used,  it  is  necessary  to  experiment 
when  a  new  brand  of  steel  is  procured,  in  order  to  as- 
certain the  proper  temperature  in  order  to  produce  the 
best  results. 

When  steel  is  heated  to  the  proper  degree,  it  may  be 
plunged  in  a  bath  of  oil  or  tallow  and  hardened,  the 
character  of  the  bath  depending  on  the  size  of  the  piece 
to  be  hardened  and  the  nature  of  the  stock  used.  For 
ordinary  purposes  a  bath  of  sperm  oil  answers  nicely. 
In  some  cases  tallow  will  be  found  to  answer  the  pur- 
pose better.  It  is  necessary  sometimes  to  add  certain 
ingredients  to  the  bath  in  order  to  get  the  required  de- 
gree of  hardness. 

The  following  is  used  by  a  concern  when  hardening 
clock  springs:  To  a  barrel  of  oil  add  lo  quarts  of 
resin  and  13  quarts  of  tallow.  If  the  springs  are  too 
hard,  more  tallow  is  added.  If,  however,  the  fracture 
indicates  granulation  of  the  steel  rather  than  excessive 

»6q 


Mixture  for  hardening  springs. 

hardness,  a  piece  of  yellow  bees'-  wax  of  about  twice 
the  size  of  a  man's  fist  is  added  to  the  above. 

The  following  mixture  has  been  used  by  the  writer 
with  success  in  hardening  springs  which,  on  account  of 
the  thickness  of  the  stock  or  a  low  percentage  of  carbon, 
would  not  harden  in  sperm  oil : 

Spermaceti  oil 48  parts. 

Neat's  foot  oil 46      ' '  I 

Rendered  beef  suet 5       ' ' 

Resin i       * ' 

The  proportion  of  the  different  ingredients  may  be 
changed  to  meet  the  requirements  of  the  particular 
job.  Resin  is  added  to  the  oil  to  strike  the  scale.  As 
the  scale  or  oxidized  surface  of  the  steel,  when  subjected 
to  heat,  is  liable  to  raise  in  the  form  of  blisters,  and  as 
these  are  filled  with  gas,  the  contents  of  the  bath  can 
not  act  readily  on  the  steel.  A  small  proportion  of 
spirits  of  turpentine  is  sometimes  added,  to  the  oil  for 
the  same  purpose,  but  as  it  is  extremely  inflammable, 
it  is  somewhat  dangerous  to  use  unless  great  care  is 
observed.  The  presence  of  resin  in  a  hardening  bath 
has  a  tendency  to  crystallize  the  steel,  and  on  this  ac- 
count is  sometimes  objectionable. 

A  very  good  method,  when  neither  resin  nor  turpen- 
tine are  used  to  strike  the  scale,  consists  in  having  a 
dish  of  soft  soap ;  or,  if  that  can  not  be  procured,  dis- 
solve some  potash  in  water,  dipping  the  steel  into  this 
before  heating.  It  has  the  effect  of  preventing  oxida- 
tion of  the  surfaces,  and  helps  to  strike  any  scale  that 
may  have  been  on  the  stock  previous  to  hardening. 

When  small  springs  are  to  be  hardened,  which,  on 
account  of  their  size,  cool  quickly,  they  can,  if  there 
are  many  of  them,  be  placed  in  tubes  and  heated  in  a 

261 


Furnace  for  heating  springs. 

furnace  of  the  description  shown  in  Fig.  152.  When 
the  pieces  are  heated  to  the  proper  temperature,  a  tube 
is  removed  and  inverted  over  a  bath.  The  contents 
should  go  into  the  bath  in  a  manner  that  insures  uni- 
form results,  that  is,  the  pieces  should  be  scattered  in 
the  bath.     If  the  tube  was  held  in  the  position  shown 


Figure  152.      Furnace  with  removable  tubes  for 
heating  springs. 


0000 

000 
0000 


Jht  D«nry  ColUrd  Co. 


at  Uy  in  Fig.  153,  the  pieces  would  go  into  the  bath  in  a 
lump;  but  if  it  were  held  as  shown  at  ^,  the  pieces 
would  become  scattered,  thus  insuring  good  results. 

When  springs  larger  than  those  previously  con- 
sidered are  to  be  hardened,  an  oven  having  some  means 
of  heating  the  articles  in  a  manner  that  keeps  them 
from  coming  in  contact  with  the  products  of  combus- 
tion should  be  used.      Any  form  of  a  muffle  having 

%6% 


An  oil  bath  for  spring  hardening. 


Figure  153. 

How  tubes  shown  ia 

Figure  152  should 

be  emptied. 


sufficient  capacity  will  do,  or  the  pieces  may  be  placed 
in  a  hardening  box,  having  ^  inch  powdered  charcoal 
in  the  bottom,  and  a  cover  placed  on  the  box — which 
need  not  be  sealed.  The  box  may  then  be  placed  in  a 
furnace  and  subjected  to  heat.  The  cover  may  be 
raised  from  time  to  time  and  the  contents  of  the  box 
noted.  This  makes  an  excellent  way  of  heating  large 
coil  springs  and  similar  articles. 

If  the  oven  is  sufficiently  large,  several  boxes  may 
be  heated  at  a  a 

time.  When  a 
spring  shows  the 
proper  tempera- 
ture,  which 
should  be  uni- 
form through- 
out, it  may  be  re- 
moved, placed  on 
a  bent  wire  and 
immersed  in  a 
bath  of  sperm  oil, 
having  a  jet  of 
oil  coming  up 
from  the  bottom, 
as  shown  in  Fig. 

154,  A  repre-  |  ^EiEp-EZIr^ 
senting  the  outer 
tank  containing 
water,  B  the  bath 
of  oil,  C  the  pump  used  in  drawing  the  heated  oil  from 
the  bath  through  the  pipe  D ;  it  is  then  forced  through 
the  coil  of  pipe  in  the  water  and  back  into  the  bath 
through  the  inlet  E.     F  is  the  catch  pan.     The  jet  of 

263 


The  DeiTy  CoUardi  €•• 


Oil  bath  for  spring  tempering. 

oil  is  forced  toward  the  top  of  the  tank,  as  shown  at  G. 
The  spring  should  be  worked  up  and  down  in  the 
bath  until  all  trace  of  red  has  disappeared,  when  it 
may  be  lowered  to  the  bottom  of  the  tank  and  left 
until  the  temperature  has  been  reduced  to  that  of 
the  contents  of  the  tank,  or  until  a  convenient  time 
comes  for  their  removal. 

As  previously  explained,  it  is  not  advisable  to  re- 
move articles  being  quenched  from  the  bath  until  they 


"The  J)erry  Collwd  Co. 


Figure  1 54.     Oil  bath  for  spring  tempering. 

are  of  a  uniform  temperature  throughout.  While  this 
procedure  might  not  make  as  much  difference  with  a 
piece  of  work  hardened  in  oil  as  one  hardened  in  water, 
yet  it  is  not  a  good  plan  to  remove  articles  from  the  bath 
until  they  are  reduced  throughout  to  the  temperature  of 
the  bath. 

In  order  that  the  contents  of  the  bath  may  be  kept  a 
uniform  temperature,  the  pump  shown  in  accompany- 
ing cut  may  be  connected  with  the  tank,  as  represented, 
the  oil  to  be  taken  from  near  the  top  and  pumped 

264 


How  to  heat  heavy  springs. 

through  the  coils  of  pipe  in  the  outer  tank,  which 
should  be  supplied  with  running  water. 

When  steel  contains  carbon  of  too  low  a  percen- 
tage to  harden  properly  in  oil  or  any  of  the  mixtures 
mentioned,  the  writer  has  used  a  bath  of  water  at,  or 
nearly  at,  the  boiling  point  (212°)  with  very  gratifying 
results.  It  may  be  found  necessary  with  certain  steels 
to  reduce  the  temperature  of  the  water  somewhat. 

Various  methods  are  employed  when  drawing  the 
temper.  The  one  more  commonly  used  than  any  other 
is  to  heat  the  spring  until  the  oil  adhering  to  the  sur- 
face catches  fire  and  continues  to  burn,  when  the  piece 
is  removed  from  the  fire,  burning  until  all  the  oil  has 
been  consumed.  If  this  method  is  used,  it  will  be 
found  necessary  to  provide  some  means  whereby  a 
uniform  heat  may  be  obtained,  or  one  part  of  the  spring 
will  be  found  to  be  too  soft  by  the  time  the  balance  is 
rightly  tempered. 

If  the  spring  is  of  heavy  stock,  it  is  necessary  to  bum 
the  oil  off  three  and  sometimes  more  times,  in  order  to 
bring  it  to  the  proper  degree  of  elasticity.  The  process 
of  drawing  the  temper  by  heating  the  spring  until  the 
oil  catches  fire  from  the  heat  contained  in  the  steel  is 
familiarly  known  as  "flashing."  Hardeners  say  that 
it  is  necessary  to  flash  oil  off  this  spring  three  times, 
or  it  is  necessary  to  flash  tallow  off  this  spring  twice, 
some  using  the  oil  the  piece  was  quenched  in,  while 
others  prefer  some  other  kind  of  oil  or  tallow. 

Springs  hardened  in  boiling  water  may  be  coated 
with  oil  or  tallow  and  the  temper  drawn  as  described, 
if  it  be  found  necessary.  It  is  not  policy  to  use  a  fire 
having  a  forced  draft  or  blast  when  drawing  articles 
to  a  spring  temper.     An  open  fire  burning  wood  or 

265 


The  thermometer  in  spring  tempering. 

charcoal  gives  excellent  results.  A  gas  flame  having 
no  air  blast  also  works  very  satisfactorily. 

Springs  of  unequal  sizes  on  the  various  portions  re- 
quire a  very  skillful  operator,  in  order  to  get  uniform 
results,  if  the  above  method  is  used.  The  thinner 
portions,  heating  faster  than  the  heavier  parts,  be- 
come too  soft  before  the  other  parts  are  soft  enough. 
Consequently,  it  is  advisable  to  temper  these  by  a  dif- 
ferent method.  The  spring  may  be  placed  in  a  per- 
forated pail,  which  in  turn  is  set  into  a  kettle  of  oil  or 
tallow.  This  kettle  is  placed  where  a  sufficient  amount 
of  heat  may  be  obtained  to  draw  the  temper  to  the 
proper  degree. 

The  amount  of  heat  given  is  gauged  by  a  ther- 
mometer, and  varies  according  to  the  nature  of  the 
steel  and  the  character  of  the  spring.  It  ranges  from 
560°  to  630°.  The  exact  amount  of  heat  necessary  must 
be  ascertained  by  experiment.  This  method  furnishes 
a  very  reliable  way  of  tempering  all  kinds  of  springs. 
The  kettle  should  be  so  arranged  that  a  cover  may 
easily  be  placed  on  it  in  case  the  oil  catches  fire,  as 
otherwise  the  operator,  or  the  building,  might  be  burned, 
or  the  work  in  the  oil  spoiled,  or  the  thermometer 
cracked.  The  cover  should  be  made  high  enough  to 
take  in  the  thermometer. 

The  cover  should  be  provided  with  a  long 
handle,  in  order  that  the  operator  may  not  be  burned 
when  putting  it  on  the  kettle.  If  it  is  not  considered 
necessary  to  provide  the  cover  mentioned,  a  piece  of 
heavy  sacking  should  be  kept  conveniently  near  for 
use.  If  this  is  placed  over  the  top  of  the  kettle,  it  will 
generally  extinguish  the  flames. 

The  thermometer  should  not  be  taken  from  the  hot 

266 


Heating  watch  springs. 

oil  and  placed  where  any  current  of  air  can  strike  it,  or 
the  glass  will  crack.  It  is  advisable  to  leave  it  in  the 
oil,  letting  it  cool  down  with  it.  If  the  furnace 
where  the  oil  is  being  heated  is  located  where  any  cur- 
rent of  air  will  strike  the  thermometer,  it  must  be  pro- 
tected in  some  manner,  or  it  will  crack. 

If  it  is  considered  advisable  to  remove  the  pail  of 
work  from  the  oil  before  the  pieces  are  cool,  it  may  be 
done,  and  the  pieces  dumped  into  a  wooden  box,  cover- 
ing the  opening,  so  that  the  air  will  not  strike  the 
pieces.  The  pail  may  now  be  filled  with  fresh  pieces 
requiring  tempering.  The  pail  of  work  should  be 
placed  in  the  kettle  of  oil.  The  kettle  should  not  be 
placed  in  the  fire  again  until  the  pieces  of  work  have 
absorbed  considerable  of  the  heat  that  was  in  the  oil, 
when  the  kettle  may  be  placed  in  the  fire  and  the 
operation  repeated. 

When  work  is  hardened  in  large  quantities,  it  is 
generally  considered  advisable  to  devise  methods  that 
allow  of  handling  the  work  cheaply,  at  the  same  time 
keeping  the  quality  up  to  the  standard.  Watch  springs 
are  sometimes  heated  in  a  crucible  containing  melted 
cyanide  of  potassium  or  salt  and  cyanide  of  potas- 
sium heated  to  the  proper  degree.  The  springs 
are  immersed  in  the  mixture  until  uniformly  heated, 
then  quenched.  It  is  stated,  however,  that  this 
mixture  will  not  do  when  heating  the  hair  springs, 
as  it  causes  the  nature  of  the  steel  to  change 
slightly.  These  springs  are  heated  for  hardening  in  a 
crucible  of  melted  glass. 

When  a  make  of  steel  is  found  that  gives  satisfac- 
tory results  when  made  into  springs  and  tempered,  it  is 
folly  to  exchange  it  for  another  make,  unless  convinced 

267 


The  "second  blue." 

that  the  other  is  better.  A  saving  of  a  few  cents,  or 
even  dollars,  on  an  order  of  steel  is  quite  often  very- 
costly  economy,  as  many  times  springs  do  not  give  out 
until  in  actual  use,  and  in  that  case  they  are  often- 
times many  miles  from  the  factory  where  they  were 
made. 

When  large  numbers  of  springs  that  must  receive 
severe  usage  are  made,  it  is  advisable  to  give  them  a 
test — at  least,  test  an  occasional  spring.  Give  them  a 
test  somewhat  more  severe  than  they  will  be  liable  to 
get  in  actual  use.  By  so  doing  it  is  possible  to  detect 
an  improper  method  of  hardening  or  tempering  before 
the  whole  batch  is  done. 

"Second   Blue-" 

When  all  springs  were  made  of  tool  steel  and 
hardened,  and  the  temper  drawn  one  at  a  time,  it  was 
customary  with  some  hardeners  to  draw  the  temper  to 
what  is  known  as  the  * 'second  blue."  After  harden- 
ing, the  springs  were  polished,  then  placed  in  a  pan  of 
sand  and  held  over  the  fire  until  the  temper  colors 
commenced  to  show,  the  pan  in  the  meantime  being 
shaken  to  keep  the  sand  and  springs  in  motion  and 
insure  uniform  heating.  The  tempers  will  show  in 
order  as  set  forth  in  the  color  table  given  under 
Drawing  the  Temper.  After  the]  colors  had  all 
appeared,  the  surface  of  the  steel  assumes  a  grayish 
appearance.  When  heated  a  trifle  above  this,  it  as- 
sumes a  blue  color  again,  which  is  known  as  the 
"second  blue."  When  this  color  appears,  the  spring 
should  be  dropped  in  a  tank  of  hot  oil,  leaving  it  to 
cool  off  with  the  oil. 

a68 


Colors  for  springs — how  obtained. 

Another  method  sometimes  used  when  drawing  the 
temper  of  heavy  springs  made  from  high  carbon  steel 
consists  in  heating  the  article  until  sawdust  dropped 
on  it  catches  fire,  or  a  fine  shaving  left  from  a  hard- 
wood stick,  such  as  a  hammer  handle,  being  drawn 
across  a  comer  of  it,  catches  fire  at  the  proper  temper- 
ing heat. 

Mechanics  are  sometimes  surprised  when  they  ob- 
serve a  spring  in  some  conspicuous  place  which  is  drawn 
to  a  straw  color,  a  brown  or  a  light  blue.  It  does  not 
seem  possible  to  them  that  a  spring  drawn  to  the  tem- 
per represented  by  the  color  visible  should  be  able  to 
stand  up  to  the  work.  The  temper  color  shown  is 
simply  for  appearance.  The  articles  are  first  hardened 
and  tempered  to  give  them  the  necessary  elasticity. 
This  is  ordinarily  done  by  heating  in  a  kettle  of  oil, 
gauging  the  heat  with  a  thermometer.  After  heating 
to  the  proper  temperature  and  cooling,  they  are 
polished.  Any  desired  color  can  be  given  by  placing 
the  articles  in  a  pan  of  sand  and  shaking  over  a  fire 
until  the  desired  color  shows,  when  they  may  be 
dumped  in  warm  oil  to  prevent  running.  This  second 
operation  does  not  affect  the  hardness  or  elasticity, 
provided  they  were  not  heated  as  hot  as  when  the 
temper  was  drawn. 

Many  times  it  is  impossible  to  harden  and  temper  a 
spring  in  a  manner  that  gives  satisfactory  results,  be- 
cause the  spring  was  bent  to  shape  when  cold.  Now, 
it  is  possible  to  bend  most  steel  somewhat  when  cold, 
and  yet  have  it  take  a  good  spring  temper ;  but  it  is 
impossible  to  bend  it  beyond  a  certain  amount,  which 
varies  with  the  steel. 

The  writer  has  seen  large  safety  valve  coil  springs 

269 


Caution  about  annealing  sheet  steel. 

rendered  unfit  for  use  by  coiling  when  cold.  If  a 
piece  of  the  same  steel  was  heated  red-hot  and  coiled, 
excellent  results  were  obtained. 

Many  times  it  is  necessary  to  anneal  steel  one  or 
more  times  between  operations  in  order  to  obtain  good 
results.  It  was  found 
necessary  to  anneal 
the  spring  shown  in 
Fig.  155  after  punch- 
ing the  blank  and 
before  bending  at  all. 
The  first  operation  of 
bending  brought  the 
spring  nearly  to 
shape ;  it  was  then  an- 
nealed, and  the  finish- 
ing operation  taken. 
If  it  was  bent  to  shape 
without  annealing 
the  second  time,  it 
would  break  in  the 
comers  when  in  use,  if  not  in  the  operations  of  bending. 

When  annealing  sheet  steely  whether  it  be  for  springs 
or  cutting  tools,  the  utmost  caution  should  be  exercised. 
If  the  steel  is  allowed  to  stay  in  a  red-hot  condition  for 
too  great  a  length  of  time,  the  stock  is  rendered  unfit 
for  hardening.  If  heated  red-hot  and  laid  aside  to  cool 
slowly^  much  better  results  will  follow  than  if  it  were 
packed  in  an  annealing  box  with  charcoal  and  kept  red- 
hot  for  a  considerable  length  of  time.  These  long 
heats  apparently  have  the  effect  of  throwing  the  carbon 
out  of  its  proper  combination  with  the  iron.  It  will 
harden,  but  can  never  be  made  elastic  or  strong. 


Tlw  Derry  C«ll»rd  Co. 

Figure  155.     A  peculiar  case. 


ayo 


Making  Tools  of  Machine 
Steel. 


6^?=^  ^?=^s£) 


CO 

While  it  is  considered  advisable  in  most  shops  to 
make  articles  whose  bearing  surfaces  must  be  hard,  in 
order  to  resist  frictional  wear,  of  some  form  of  machine 
steel,  and  give  the  surfaces  sufficient  hardness  by  case 
hardening,  it  is  generally  considered  necessary  to  make 
cutting,  forming  and  similar  tools  of  tool  steel. 

It  is  practical,  however,  to  make  cutting  tools  for 
certain  classes  of  work  of  machine  steel,  and  harden  the 
cutting  edges  sufficiently  to  produce  very  satisfactory 
results. 

Steel  is,  as  previously  explained,  a  combination  of 
iron  and  carbon.  The  grade  of  iron  used  in  making 
tool  steel  is,  however,  vastly  superior  and  much  more 
expensive  than  that  used  in  the  manufacture  of  the  or- 
dinary machine  steel.  Being  much  purer,  it  is  much 
stronger  when  carbonized  and  hardened,  and  conse- 
quently can  do  many  times  the  amount  of  work  of  tools 
made  of  the  lower  grades  of  steel,  even  when  these  are 
charged  with  the  satnc  percentage  of  carbon.  It  is  also 
less  liable  to  crack  when  hardened,  as  the  impurities 
contained  in  the  lower  grades  make  it,  when  combined 
with  carbon,  very  brittle  when  hardened. 

But  notwithstanding  the  facts  just  presented,  it  is 
471 


How  phosphorus  affects  steel. 

possible  to  make  tools  for  cutting  paper,  wood,  lead, 
brass  and  soft  steel  of  a  low  grade  of  steel,  and  harden 
it  by  a  process  that  gives  results  much  more  satisfac- 
tory than  would  be  thought  possible  by  one  who  had 
never  tried  it.  This  method  recommends  itself  on  ac- 
count of  the  comparatively  low  cost  of  the  steel,  and  it 
can  be  worked  to  shape  more  cheaply  than  if  tool  steel 
were  used.  But  it  is  usual,  when  the  experiment  is 
tried,  to  use  any  piece  of  low  grade  steel  laying  around 
the  shop  that  will  machine  to  shape  in  a  satisfactory 
manner,  not  realizing  that  it  is  necessary,  in  order  to 
get  satisfactory  results,  to  use  steel  adapted  to  the  pur- 
pose. As  phosphorus,  when  present  in  steel,  and  es- 
pecially when  in  combination  with  carbon,  causes  it 
to  be  extremely  brittle  when  hardened,  a  grade  should 
be  selected  that  has  the  least  possible  percentage  of  this 
harmful  impurity. 

If  it  is  not  necessary  to  have  the  hardened  surface 
very  deep,  a  steel  having  a  low  percentage  of  carbon 
may  be  used.  If,  however,  the  tool  is  to  be  subjected 
to  great  strains,  it  is  advisable  to  use  a  steel  containing 
sufficient  carbon  to  cause  the  tool  to  harden  enough  to 
furnish  the  necessary  stiffness  or  internal  hardness. 
The  extra  amount  of  hardness  necessary  to  insure  the 
cutting  portions  standing  up  when  in  use,  must  be  fur- 
nished by  the  process  of  hardening. 

The  writer  has  seen  reamers,  counterbores,  punch 
press  blanking,  forming  and  drawing  dies,  and  many 
other  forms  of  tools  made  of  low  grade  steel,  which, 
the  parties  using  them  claimed,  gave  the  best  of  results. 

As  before  stated,  when  making  tools  which  are  not 
to  be  subjected  to  a  very  great  amount  of  strain,  or 
which  will  not  be  called  upon  to  resist  a  great  amount 

^^^ 


Steel  for  slender  tools. 

of  pressure,  a  steel  low  in  carbon  may  be  used.  Any 
desired  amount  of  surface  hardness  may  be  given  the 
piece.  If,  however,  the  tool  will  be  subjected  to  tor- 
sional strain,  as  in  the  case  of  a  long,  slender  reamer, 
or  if  it  may  have  to  resist  a  crushing  strain,  as  in  the 
case  of  a  punch  press  forming  die,  it  is  necessary  to  use 
stock  containing  sufficient  carbon  to  furnish  the  desired 
result  when  hardened.  If  the  tool  is  not  to  be  subjected 
to  very  great  strain,  almost  any  low  grade  stock  that  is 
practically  free  from  impurities  will  do. 

If  a  long,  slender  reamer,  or  similar  tool,  is  to  be 
made,  excellent  results  are  claimed  by  using  a  low 
grade  steel  of  40-point  (.405^)  carbon.  In  the  case  of  a 
forming  die,  or  similar  tool,  use  a  steel  of  60  to  80-point 
carbon.  If,  however,  it  was  to  be  subjected  to  great 
pressure  or  very  severe  usage,  the  writer's  experience 
leads  him  to  advocate  the  use  of  tool  steel  specially 
adapted  to  this  class  of  work. 

As  it  is  necessary,  in  order  to  get  satisfactory  re- 
sults, to  have  the  percentage  of  impurities  as  low  as 
can  be  obtained,  in  order  to  have  the  hardened  steel  as 
strong  as  possible,  do  not  allow  it  to  come  in  contact 
with  any  form  of  bone  when  heating.  The  articles  should 
be  packed  in  a  hardening  box  with  a  mixture  of  equal 
quantities  (volume)  of  charred  leather  and  granulated 
charcoal  in  the  same  manner  as  described  under  Pack 
Hardening.  It  will  be  necessary  to  subject  the  articles 
to  heat  for  a  longer  period  of  time  than  if  hardening 
tool  steel.  The  length  of  time  the  articles  are  sub- 
jected to  the  action  of  the  carbonizing  element  depends 
on  how  deep  it  is  necessary  to  have  the  hardened  portion. 
The  test  wires  previously  mentioned  should  be  used 
to  determine  when  the  contents  of  the  box  are  heated. 

a73 


When  in  doubt  about  steel. 

If  you  are  reasonably  sure  the  steel  used  was  prac- 
tically free  from  injurious  impurities  and  is  low  in  car- 
bon, it  may  be  dipped  in  a  bath  of  water  or  brine. 
Should  there  be  any  doubt  as  to  this,  dip  in  raw  lin- 
seed oil. 

If  the  article  being  hardened  is  a  cutting  tool,  or 
something  requiring  a  fine,  compact  grain,  better  re- 
sults will  follow  if  it  is  left  in  the  box  after  being  sub- 
jected to  the  action  of  carbon,  the  box  removed  from 
the  fire,  and  the  whole  allowed  to  cool.  When  cold, 
the  article  may  be  reheated  to  a  low  red,  and  hardened. 

While  the  writer  has  used  a  low  grade  steel  in 
making  various  forms  of  tools,  and  had  excellent  re- 
sults when  they  were  put  to  the  use  for  which  they 
were  intended,  he  cannot  recommend  its  use,  unless  the 
parties  doing  the  work  select  stock  suited  to  the  pur- 
pose and  exercise  due  care  when  hardening. 

While  this  subject  might  properly  be  classed  under 
the  heading  of  Case  Hardening,  it  has  not  seemed  wise 
to  the  writer  to  do  so,  because  case  hardening,  according 
to  the  interpretation  usually  given  it  by  mechanics,  is 
simply  a  process  of  transforming  the  surface  of  the 
article  into  a  condition  that  allows  it  to  become  hard  if 
plunged  red-hot  into  water.  Hardness  is  apparently 
the  only  object  sought,  but  such  is  not  the  case  when 
the  subject  is  considered  in  its  proper  light. 

When  applying  this  principle  to  tools,  it  is  neces- 
sary to  consider  the  requirements  of  the  tools.  Know- 
ing this,  it  is  necessary  to  proceed  in  a  manner  that 
will  give  the  desired  results. 

If  it  is  considered  advisable  to  make  certain  tools 
of  a  low  grade  steel,  treating  it  as  described,  it  is 
necessary  to  select  steel  adapted  to  the  tool  to  be  made. 

274 


special  steels. 

It  is  never  advisable  to  use  Bessemer  steel  bought  in 
the  open  market,  because  it  does  not  run  uniform. 
Always  use  open  hearth  steel,  procuring  it,  if  possible, 
of  a  quality  that  will  give  satisfactory  results.  Steel, 
with  a  very  small  percentage  of  phosphorus  and  other 
impurities,  may  be  obtained  from  any  reliable  maker, 
if  the  purpose  for  which  it  is  to  be  used  is  stated  when 
ordering. 

Special  Steels. 


To  one  interested  in  working  steel,  the  history  of 
the  development  of  this  industry  furnishes  a  remarka- 
bly interesting  study. 

Steel  may  be  grouped  under  four  general  heads, 
the  name  given  each  class  being  selected  on  account  of 
the  method  pursued  in  its  manufacture. 

Probably  the  oldest  of  all  known  steels  is  the 
cemented  or  converted  steel.  This  steel  is  made  by 
taking  iron  in  the  form  of  wrought  iron  bars,  packing 
them  in  a  fire-brick  receptacle,  surrounding  each  bar 
with  charcoal.  This  is  hermetically  sealed,  and  heat 
is  then  applied  until  the  whole  is  brought  to  a  degree 
of  heat  that  insures  the  penetration  of  a  sufficient 
quantity  of  carbon.  Experience  proves  that  carbon 
will  penetrate  iron  at  about  the  rate  of  one-eighth  of 
an  inch  in  twenty-four  hours;  and  as  bars  of  about 
three-quarter  inch  thickness  are  generally  used,  it  re- 
quires three  days  for  the  carbon  to  penetrate  to  the 

»75 


Crucible  cast  steel. 

center  of  the  bar  (^-inch).  The  furnace  is  then  al- 
lowed to  cool,  and  the  iron  bars,  which  are  converted 
to  steel,  are  removed.  They  are  found  to  be  covered 
with  blisters,  hence  the  name.  Blister  Steel. 

When  examined,  the  bars  are  found  to  be  highly- 
crystalline,  brittle  steel.  When  this  form  of  steel  is 
heated  and  rolled  directly  into  commercial  bars,  it  is 
known  as  German  Steel. 

If  blister  steel  is  worked  by  binding  a  number  of 
bars  together,  heating  to  a  high  heat,  and  welded  under 
a  hammer,  it  is  known  as  Shear  Steel,  or  Single- Shear. 

If  single-shear  steel  is  treated  as  above,  the  finished 
product  is  known  commercially  as  Double- Shear  Steel. 

Until  within  a  comparatively  few  years  these  three 
classes  of  converted  steel  were  practically  the  only 
kinds  known  in  commerce. 

Crucible   Cast   Steel. 

As  this  is  the  standard  steel  used  for  fine  tools,  a 
brief  study  of  the  methods  used  in  its  manufacture 
may  be  of  interest  to  the  reader.  Benjamin  Huntsman, 
a  clockmaker,  is  supposed  to  have  been  the  inventor  of 
this  process.  It  occurred  to  him  that  he  might  pro- 
duce a  more  uniform  and  satisfactory  article  than  was 
to  be  had  at  that  time  for  use  in  manufacturing  springs 
to  run  his  clocks.  The  method  he  had  in  mind  con- 
sisted in  charging  into  a  crucible  broken  blister  steel, 
v^^hich  was  melted  to  give  it  a  homogeneous  character. 

While  Huntsman  thus  founded  the  crucible  steel 
industry,  which  has  been  of  incalculable  value  to  the 
mechanic  arts,  he  met  with  many  difficulties.  These 
have  been  overcome  by  later  inventions,  notably  those 

276 


Alloy  steels. 

of  Heath  and  Mushet,  until  to-day  it  is  possible,  with 
skill  and  care,  to  produce  a  quality  of  steel  which,  for 
strength  and  general  utility,  has  never  been  equaled, 
despite  the  claims  of  some  blacksmiths  that  the  steel  of 
to-day  is  not  as  good  as  that  produced  25  to  50  years  ago. 
Competition  has  rendered  it  necessary  to  run  cut- 
ting tools,  or  stock,  as  the  case  may  be,  much  faster 
than  was  formerly  the  case,  which  made  it  necessary  to 
make  steel  containing  a  higher  percentage  of  carbon 
than  was  formerly  the  case.  As  stated  in  a  previous 
chapter,  when  high  carbon  steels  are  used,  it  is  neces- 
sary to  exercise  great  care  in  heating  for  the  various 
processes  of  forging,  annealing  and  hardening.  As 
high  carbon  steels  are  more  easily  burned  than  those 
containing  a  lower  percentage,  it  is  necessary  to  put 
them  in  the  hands  of  skilled  workmen,  for,  unless  the 
steel  is  to  be  worked  by  men  understanding  its  nature, 
it  proves  to  be  a  very  unsatisfactory  investment,  and 
is  often  condemned  because  it  will  not  stand  as  much 
abuse  as  a  steel  of  lower  carbon;  but  if  properly 
treated,  will  do  many  times  the  amount  of  work. 


Alloy   Steels. 


In  order  to  accomplish  certain  results,  steel  is  made 
containing  other  metals.  To  distinguish  them  from 
steels,  which  depend  on  the  quantity  of  carbon  present 
for  their  hardening  properties,  they  may  properly 
be  termed  "alloy"  steels,  the  amount  of  the  hardening 
property  present  determining  the  quality  of  the 
steel.  As  these  steels  can  generally  be  run  at  a  higher 
periphery  speed  and  cut  harder  metals  than  carbon 
steels,  they  are  very  valuable  at  times,  and  in  some 

277 


Self-hardening  steel. 

shops  are  used  altogether.  As  a  rule,  they  are  more 
easily  injured  by  fire  than  carbon  steel,  and,  conse- 
quently, extreme  care  must  be  exercised  when  working 
them. 

When  high  carbon  steel  is  alloyed  with  other  hard- 
ening properties,  a  steel  is  produced  which  will  be  found 
more  efficient  for  machining  chilled  iron  than  the 
regular  high  carbon  steels.  However,  as  the  nature  of 
steel  of  this  character  depends  entirely  on  the  amount 
and  kind  of  the  alloy  used  and  the  amount  of  carbon 
present,  no  fixed  rule  can  be  given  for  the  treatment. 
It  is  always  best  to  follow  as  closely  as  possible  direc- 
tions received  with  the  steel. 

The  writer  has  seen  milling  machine  cutters,  punch 
press  blanking  dies,  and  other  tools,  which  were  to  cut 
very  hard,  "spotty"  stock,  give  excellent  results,  when 
made  from  a  reliable  alloy  steel,  where  carbon  steels 
would  not  stand  up. 

If  the  amount  of  certain  hardening  elements  be 
increased  to  a  given  point,  the  steel  hardens  when 
heated  red-hot,  and  is  exposed  to  the  air.  It  is  styled 
**Air  Hardening  Steel,"  more  generally  known,  how- 
ever, as  Self-Hardening  Steel. 

Self-hardening  Steel. 

It  was  not  originally  the  intention  of  the  writer  to 
mention  self -hardening  steel,  because  there  are  so  many 
different  makes  of  the  article,  each  differing  from  the 
other  to  an  extent  that  the  method  employed  to  get  sat- 
isfactory results,  when  using  one  make,  would  prove 
entirely  unsatisfactory  when  applied  to  another. 

Self-hardening  steel  has  a  field  of  its  own,  and  is 
very  useful  when  made  into  tools  for  certain  work.     It 

278 


A  common  error. 

is  used  very  extensively  in  cutting  hard  metals,  and 
can  be  run  at  a  high  periphery  speed,  because  the  heat 
generated  does  not  soften  the  tool,  as  is  the  case  when 
carbon  steels  are  used. 

No  general  instructions  can  be  given  for  working 
the  steel,  because  the  composition  of  the  different  makes 
varies  so  much  that  the  treatment  necessary,  in  order 
that  one  brand  may  work  satisfactorily,  would  unfit 
another  for  doing  the  maximum  amount  of  work  pos- 
sible for  it  to  do. 

A  very  common  error  in  shops  where  a  make  of 
this  steel  is  used,  and  another  brand  is  to  be  tried,  con- 
sists in  attempting  to  treat  the  new  brand  in  the  same 
manner  they  have  been  treating  the  other,  regardless 
of  instructions  furnished. 

As  previously  stated,  the  treatment  suited  to  one 
brand  would  render  another  unfit  for  use,  and  as  the 
reputation  of  a  brand  depends  on  the  results  attained, 
the  makers  are  very  careful  when  selling  steel  to  state 
plainly  the  treatment  it  should  receive.  The  buyer 
should  see  that  the  directions  are  followed  implicitly. 

When  purchasing  self-hardening  steel,  it  is  advisa- 
ble to  investigate  the  merits  of  the  different  makes.  In 
practice,  certain  brands  prove  best  for  cutting  cast 
iron,  while  another  brand,  which  will  not  do  as  much 
work  when  cutting  cast  iron,  proves  to  be  more  desira- 
ble when  working  steel.  Other  brands,  which  give  sat- 
isfaction when  made  into  lathe  and  planer  tools,  prove 
useless  when  made  into  tools  having  projecting  cutting 
teeth,  as  milling  machine  cutters,  etc. 

As  previously  stated,  the  different  makes  of  self- 
hardening  steel  require  different  methods  of  treatment. 
One  gives  best  results  when  worked  (forged)  at  a  full 

279 


A  few  don*ts. 

red  heat,  while  another  requires  a  much  higher  heat. 
As  the  steel  is  less  plastic  when  red-hot  than  most 
carbon  steels,  it  is  necessary  to  use  greater  care  in  re- 
gard to  the  manner  in  which  it  is  hammered.  A  heavy 
hammer  should  be  used,  if  a  large  section  is  to  be  forged, 
as  it  is  necessary  to  have  it  act  uniformly  on  the  entire 
mass,  or  the  surface  portion  will  be  drawn  away  from 
the  interior,  and,  as  a  consequence,  a  rupture  will  be 
produced.  Small  pieces  should  be  forged  with  lighter 
blows,  or  the  steel  will  be  crushed. 

Do  not  attempt  to  forge  when  the  temperature  is 
lowered  to  a  point  where  the  steel  loses  its  malleability, 
or  it  will  be  injured. 

It  is  very  necessary  that  a  uniform  heat  be  main- 
tained throughout  the  piece.  Do  not  think,  when  work- 
ing a  small  section,  that  it  is  safe  to  forge  when  it  has 
cooled  to  a  low  red,  because  some  heavier  portion  has 
not  cooled  below  a  full  red. 

Do  not  allow  the  steel  to  cool  off  from  the  forging 
heat.  After  forging,  place  the  piece  in  the  fire  again, 
and  allow  it  to  come  to  a  uniform  bright  red.  Do  not 
allow  it  to  **soak"  in  the  fire,  but  it  should  be  heated 
at  this  time  without  the  aid  of  the  blast.  When  it  has 
reached  a  uniform  red  heat,  remove  from  the  fire,  and 
allow  it  to  cool  in  a  dry  place,  not  exposed  to  the  action 
of  any  draft. 

While  most  self -hardening  steels  will  become  hard 
enough  when  cooled  in  the  air,  it  is  sometimes  necessary 
to  have  the  tool  extra  hard.  In  such  cases,  it  may  be 
cooled  in  a  forced  blast.  Some  steels  give  better  re- 
sults if  cooled  in  oil,  others  require  cooling  in  hot  oil, 
while  others  may  be  cooled  in  hot  or  cold  water.  Gen- 
erally speaking,  however,  it  is  not  advisable  to  bring 

280 


Different  steels  need  different  treatment. 

most  brands  of  this  steel  in  contact  with  water  when 
red-hot. 

While  it  is  generally  admitted  that  self-hardening 
steels  are  principally  valuable  for  lathe,  planer,  and 
similar  tools,  when  cutting  hard  metals  or  running  at 
high  speeds,  there  are  makes  which  give  excellent  sat- 
isfaction when  annealed  and  made  into  such  tools  as 
milling  machine  and  similar  cutters. 

When  it  is  necessary  to  have  the  stock  in  an  an- 
nealed condition,  it  is  advisable  to  procure  it  in  this 
state,  as  the  manufacturer,  understanding  the  composi- 
tion and  nature  of  the  steel,  is  in  a  position  to  anneal 
it  in  a  more  satisfactory  manner  than  the  novice.  How- 
ever, if  it  is  considered  advisable  to  anneal  it  in  the 
factory  where  it  is  to  be  worked,  it  may  be  accom- 
plished. Different  makes  of  steel  require  treatments 
differing  from  each  other,  the  treatment  depending  on 
the  element  used  to  give  it  its  hardening  qualities. 
Some  brands  may  be  annealed  sufHciently  to  work  in 
the  various  machines  used  in  working  steel  to  shape 
by  heating  to  a  bright  red  and  burying  in  green  pine 
sawdust,  allowing  it  to  remain  in  the  sawdust  until  cool. 

Most  brands  may  be  annealed  by  keeping  the  steel 
in  an  annealing  furnace  at  a  bright  red  heat  for  from 
twenty- four  to  forty  hours,  then  covering  with  hot  sand 
or  ashes  in  the  furnace,  and  allowing  to  cool.  It  should 
be  about  the  same  length  of  time  cooling  as  it  was  ex- 
posed to  the  heat.  It  is  necessary  many  times  to 
machine  it  with  tools  made  of  the  same  quality  of  steel, 
on  account  of  the  natural  hardness  and  density  of  the 
stock.  It  is  claimed  that  tools  made  of  certain  brands 
of  self-hardening  steel  give  better  results  when  cutting 
chilled  iron  than  tools  made  of  high  carbon  alloy  steels. 

28X 


Get  reliable  steel. 

The  writer  cannot  substantiate  this  claim,  as  he  has 
never  been  able  to  get  as  good  results  as  when  using  an 
extra  high  carbon  alloy  steel,  properly  treated. 

However,  it  is  safe  to  say  that  used  for  machining 
(roughing)  work  in  the  lathe,  planer,  and  similar 
machines,  can  be  made  to  do  many  times  the  amount 
of  work  in  a  given  time  than  would  be  the  case  were 
ordinary  carbon  steel  tools  used. 

Much  better  results  may  be  attained,  however,  than 
is  usually  the  case,  if  makers*  instructions  are  implicitly 
followed. 

On  account  of  the  rapidly  growing  popularity  of 
certain  makes  of  this  class  of  steel,  many  swindles 
have  been  perpetrated  by  unscrupulous  parties,  claim- 
ing to  be  representatives  of  a  reliable  house.  A  tool 
made,  as  they  claim,  from  the  steel  they  were  selling 
is  submitted  for  trial.  It  proves  to  be  all  that  could 
be  asked  for,  and  a  quantity  of  steel  is  ordered  sent 
C.  O.  D.  When  this  is  received  and  paid  for,  it  is  found 
to  be  of  no  use.  Parties  purchasing  steel  of  any  but 
known  and  reliable  steel  concerns  do  so  at  a  great  risk,  as 
a  number  of  manufacturers  have  found  to  their  sorrow. 

Steel  for  Various  Tools. 


There  is  no  one  topic  connected  with  this  work  that 
caused  the  writer  so  much  anxiety  as  the  one  under 
consideration,  because  a  temper  of  steel  that  gives  en- 
tire satisfaction  when  used  in  one  shop,  would  not 
answer  when  made  into  tools  intended  for  the  same,  or 

282 


Phosphorus  in  steels. 

similar  purposes,  in  a  shop  situated  on  the  opposite 
side  of  the  street.  This  is  simply  because  in  one  case 
the  operator  who  forged  or  hardened  the  tools  under- 
stood handling  the  steel,  and  in  the  other  case  a  man 
totally  incompetent  was  entrusted  to  do  the  work. 

Then  again,  steels  of  certain  makes  are  more  free 
from  harmful  impurities  than  others.  A  steel  contain- 
ing a  low  percentage  of  these  impurities  can  safely  have 
a  higher  percentage  of  carbon.  Certain  steels  which 
are  low  in  their  percentage  of  phosphorus  can  have  a 
greater  amount  of  carbon  than  other  steels  which  con- 
tain more  of  this  harmful  impurity. 

A  tool  made  of  1.4  per  cent,  carbon  steel  low  in 
phosphorus  will  not  cause  as  much  trouble  as  if  made 
of  a  1.25  per  cent,  carbon  steel  containing  a  greater 
amount  of  phosphorus,  but  its  capacity  for  cutting  hard 
metals,  and  holding  its  edge  when  running  at  high 
speeds,  is  much  greater. 

Knowing  the  tendency  in  many  shops  to  use  a  high 
carbon  steel,  and  realizing  the  advantages  of  so  doing, 
the  writer  would  advocate  the  use  of  such  steels,  were 
it  not  for  the  fact  in  many  cases  the  results  have  been 
anything  but  satisfactory,  because  men  totally  unfit  for 
such  work  were  employed  to  forge  and  harden  the  tools 
made  from  them. 

But  it  has  seemed  wise  to  give  the  tempers  of  tool 
steel  suited  for  certain  purposes,  the  reader  bearing  in 
mind  that  in  many  cases  it  is  safe  and  advisable  to  use 
a  higher  carbon,  provided  due  care  is  exercised  when 
working  it  during  the  various  operations  of  forging, 
annealing  and  hardening.  As  previously  stated,  steel 
of  a  certain  make  and  temper  giving  excellent  results 
in  one  shop  does  not  always  give  satisfactory  results  in 

Z83 


The  degrees  of  hardness. 

some  other  shop  on  the  same  class  of  work.  Knowing 
from  experience  that  the  variable  factor  is  the  man 
working  the  steel,  rather  than  the  steel  itself,  the  writer 
has  deemed  it  wise  to  quote  the  experience  of  various 
steel  makers,  rather  than  results  of  his  own  personal 
experience. 


Degree  of  Hardness 

Percent- 
age of 
Carbon 

Should  be  used  for 

Very  hard 

1-5 

Turning  and  planing  tools  for 
hard    metals,     small    drills, 

gravers. 

Hard 

1.25 

Tools  for  ordinary  turning  and 
planing,  rock  drills,  mill 
picks,  scrapers,  etc. 

Medium  hard 

1. 

Taps,  screw  thread  dies, 
broaches,  and  various  tools 
for  blacksmiths'  use. 

Tenaciously  hard 

•85 

Cold  sets,  hand  chisels,  ream- 
ers, dies,  drills. 

Tough 

•75 

Battering  tools,  cold-sets,  shear 
blades,  drifts,  hammers,  etc. 

Soft 

•6s 

Battering  tools,  tools  of  dull 
edge,  weld  steel  for  steeling 
finer  tools,  etc. 

While  the  foregoing  table  gives  the  tempers  of 
steel  that  can  safely  be  used  for  the  purposes  specified, 
it  is  many  times  advisable  to  use  steel  of  a  higher  per- 
centage of  carbon. 

Then  again,  it  is  sometimes  best  to  use  a  low  carbon 
steel  of  good  quality,  in  order  to  get  the  maximum 
amount  of  toughness  in  the  interior  portions,  packing 
the  finished  tool  in  a  box  containing  charred  leather,  as 

284 


How  to  make  steel  extremely  hard. 

explained  under  Pack  Hardening,  and  running  for  a 
sufficient  length  of  time  to  get  an  extremely  hard  sur- 
face when  hardened.  By  adopting  this  method,  it  is 
possible  to  get  a  cutting  surface  that  will  stand  up  when 
running  at  a  high  rate  of  speed,  and  yet  be  strong 
enough  to  resist  extremely  rough  usage. 

When  it  is  desirable  to  get  the  steel  extremely  hard 
and  very  deep,  in  order  to  allow  for  grinding,  and  yet 
have  the  tool  sufficiently  tough  to  stand  up,  use  a  high 
carbon  steel,  pack  in  a  box  as  described,  running  in  the 
iire  at  an  extremely  low  heat ;  quench  in  a  bath  of  raw 
linseed  oil. 

In  order  to  provide  a  guide  for  use  in  selecting 
steel  suitable  for  various  purposes,  the  following  list 
is  given.  It  is  the  result  of  the  writer's  experience,  and 
information  picked  up  here  and  there.  A  very  notice- 
able fact,  however,  must  be  taken  into  consideration, 
namely:  mechanics  in  the  same  class  do  not  advocate 
the  use  of  steel  of  like  tempers,  even  when  making  tools 
of  the  same  kind,  to  do  the  same  class  of  work  under 
the  same,  or  similar  circumstances,  so  no  rule  can  be 
given  arbitrarily. 

The  reader  should,  however,  bear  in  mind  that 
steels,  which  contain  impurities  to  any  considerable  de- 
gree, cannot  safely  be  used  with  the  percentage  of 
carbon  mentioned.  But  as  most  of  the  leading  steels 
on  the  market  have  received  their  standing  because  they 
are  practically  free  from  these  impurities,  it  is  safe 
when  using  them  to  use  the  percentages  of  carbon 
mentioned. 

There  are  several  makes  of  crucible  tool  steel 
on  the  market,  which  are  exceptionally  low  in  their 
percentage  of  impurities,  and  when  using  these,  it  is 

285 


About  cast  steel. 

safe  to  use  a  higher  carbon  than  the  one  mentioned, 
provided  due  care  is  used  when  heating  for  the  various 
operations  of  forging,  annealing  and  hardening. 

In  the  following  pages  the  term  crucible  steel  is 
intended  to  denote  crucible  tool  cast  steel. 

The  term  cast  steel  is  often  misunderstood  by  me- 
chanics, and  many  are  of  the  opinion  that  any  cast  steel 
is  tool  steel.  Such,  however,  is  not  the  case,  for  the 
products  of  the  Bessemer  and  open  hearth  processes 
are  cast  steel  in  the  same  sense  that  crucible  steel 
is,  yet  they  are  not  understood  as  tool  steels,  although 
products  of  both  processes  which  were  highly  carbon- 
ized have  been  sold  to  parties  as  tool  steel. 

Arbors  for  saws. 
Saw  arbors,  and  similar  articles,  when  made  from 
crucible  steel  are  made  from  a  stock  containing  .60  to 
.70  per  cent,  carbon.  When  made  from  open  hearth 
steel  the  percentage  of  carbon  is  about  the  same, 
although  some  manufacturers  claim  good  results  when 
a  lower  percentage  is  used. 

Arbors  for  milling  machines. 
Milling  machine  arbors  when  made  from  crucible 
steel  give  good  satisfaction  if  a  steel  of  .70  to  .80  per 
cent,  carbon  is  used.  Unless  they  are  to  be  hardened, 
better  results  are  obtained  if  the  steel  is  worked  to 
shape  without  annealing,  as  it  is  much  less  liable  to 
spring  when  subjected  to  strain  in  use.  In  shops  where 
great  numbers  of  these  arbors  are  used  crucible  steel 
is  considered  very  costly.  In  such  cases  open  hearth 
steel  containing  .40  to  .60  per  cent,  carbon  is  often 
used.  Many  times  a  stock  containing  a  higher  per- 
centage is  used. 


Augers. 
Augers   for  wood-work   are   made   from  crucible 
steel  of  .70  to  .80  per  cent,  carbon. 

Axes 

are  made  from  crucible  steel  containing  i.oo  to  1.20 
per  cent,  carbon. 

Barrels  for  Guns 

are  made  from  crucible  steel  containing  .60  to  .70  per 
cent,  carbon,  while  some  manufacturers  use  an  open 
hearth  steel  containing  .50  per  cent,  carbon,  and  others 
claim  to  use  the  same  steel  with  .  60  or  even  .  70  per  cent. 

Centers  for  Lathes 

are  made  of  crucible  steel  containing  .90  to  i.io  per 
cent,  carbon. 

Chisels  for  Working  Wood 
are  made  from  crucible  steel  containing  1.15  to  1.25 
per  cent,  carbon. 

Chisels  for  Cutting  Steel, 

where  the  work  is  light,  give  good  satisfaction  when 
made  from  crucible  steel  containing  1.25  per  cent, 
carbon. 

Cold  Chisels, 

for  chipping  iron  and  steel,  work  well  if  made  from 
crucible  steel  containing  .90  to  i.io  per  cent,  carbon. 
Trouble  with  cold  chisels  is  more  often  the  result  of 
poor  workmanship  than  an  unsatisfactory  steel. 

Chisels  for  Hot  Work 

may  be  made  of  crucible  steel  of  .60  to  .70  per  cent, 
carbon. 

a87 


Chisels  for  Cold  Work, 

for  blacksmiths'  use,  are  made  of  crucible  steel  con- 
taining  .70  to  .80  per  cent,  carbon. 

Chisels  for  Cutting  Stone 
are  made  from  .85  per  cent,  carbon  crucible  steel. 

Cutters  for  Milling  Machine  Work 

are  probably  made  from  a  greater  range  of  tempers  than 
almost  any  other  tool  used  in  machine  shop  work, 
some  manufacturers  never  using  a  steel  containing  over 
1. 00  per  cent,  of  carbon,  on  account  of  the  liability  of 
cracking.  Cracking  is,  however,  a  result  of  careless 
working,  and  as  much  more  work  can  be  done  in  a  given 
time  with  a  cutter  made  from  a  high  carbon  steel,  it 
is,  generally  speaking,  advisable  to  use  such  steels. 
Cutters,  2  inches  and  smaller,  may  safely  be  made  from 
crucible  steel  containing  1.25  to  1.40  per  cent,  carbon. 
Cutters,  2  to  3  inches,  1.15  to  1.25.  Larger  than  3 
inches,  or  if  of  irregular  contour,  1. 10  to  i.  20  per  cent, 
carbon.  There  are  several  alloy  steels  on  the  market 
which  give  excellent  results  when  made  into  cutters  of 
this  character,  provided  extreme  care  is  taken  in 
heating. 

Cutters  for  Pipe  Cutting 

may  be  made  from  crucible  steel  containing  1.20  to 
1.25  per  cent,  carbon. 

Cutters  for  Glass 

are  made  from  crucible  steel  containing  1.25  to  1.40 
per  cent,  carbon. 

288 


Dies  (Threading)  for  Bolts 

and  similar  work,  made  from  stock  having  rough,  un- 
even surfaces,  may  be  made  from  crucible  steel  con- 
taining .  70  to  .  80  per  cent,  carbon.  However,  when  the 
dies  are  hardened  by  the  process  described  under  Pack 
Hardening,  steel  containing  i.ooto  i.io  percent,  works 
nicely,  stands  well,  and  holds  a  good  edge. 

Dies  for  Screw  Cutting, 

to  be  used  by  hand  or  in  screw  machine,  may  be  made 
from  crucible  steel  containing  i.oo  to  1.25  per  cent, 
carbon. 

Dies  for  Blanking  or  Punch  Press 
work  are  made  from  crucible  steel  containing  .90  to 
I.IO  per  cent,  carbon.  When  the  articles  to  be  punched 
are  small,  and  the  stock  to  be  worked  is  hard,  steel  con- 
taining 1.00  to  1.25  stands  better  than  the  lower  carbon 
steel  for  small  dies.  Some  manufacturers  use  a  steel 
containing  1.25  to  1.40  per  cent,  carbon,  provided  it  is 
low  in  percentage  of  impurities.  When  the  work  is 
not  of  a  shape  that  requires  great  strength  on  the  part 
of  the  die,  open  hearth  steel  containing  .40  to  .80  per 
cent,  carbon  is  used.  The  die  in  this  case  should  be 
hardened  according  to  directions  given  for  hardening 
tools  made  from  machine  steel. 

Dies  Used  for  Swaging 

metals  are  made  from  crucible  steel,  the  percentage  of 
carbon  varying  according  to  the  character  of  the  work 
to  be  done.  When  the  die  is  not  to  be  subjected  to 
very  severe  usage,  a  steel  containing  .90  to  i.io  per 
cent,  of  carbon  may  be  used.  Where  a  deeply  hard- 
ened portion  is  desirable,  a  steel  containing  1.20  to  1.25 
per  cent,  works  nicely. 

289 


Drawinrr  Dies 

o 

are  made  of  crucible  steel  containing  1.20  to  1.25  per 
cent,  carbon. 

Dies  for  Drop   Forging. 

As  the  product  of  different  steel  manufacturers 
varies  so  much,  and  the  requirements  are  so  varied  for 
work  of  different  kinds,  it  is  advisable  to  submit  the 
article  to  be  made  to  some  reliable  steel  manufacturer, 
letting  him  furnish  a  steel  especially  adapted  to  the 
work  to  be  done.  Ordinarily  a  crucible  steel  is  used 
containing  .40  to  .80  per  cent,  carbon.  However,  many 
manufacturers  consider  it  best  to  use  a  good  quality  of 
open  hearth  steel  containing  the  proper  percentage  of 
carbon.  Small  dies,  or  those  having  slender  portions 
requiring  great  strength,  are  made  of  the  higher  carbon. 

Drills— (Rock  Drills), 

for  quarry  work,  are  made  of  crucible  steel  containing 
1. 10  to  1.25  per  cent,  carbon. 

Drills— (Twist). 

Sma//  drills  are  made  of  crucible  steel  of  1.25  to 
1. 50  per  cent,  carbon,  while  larger  drills  require  a  steel 
of  1. 00  to  1.25. 

Files 

are  made  of  crucible  steel  of  1.20  to  1.40  per  cent,  car- 
bon. Files  of  inferior  quality  are  made  of  open  hearth 
steel. 

Hammers  for  Blacksmiths 

use  are  made  from  crucible  steel  of  .65  to  .75  per  cent, 
carbon. 

S90 


Hammers  for  Machinists' 

use  are  made  from  crucible  steel  of  .85  to  1.15  per 
cent,  carbon.  For  the  ordinary  sizes  steel  containing 
1. 00  per  cent,  works  nicely. 

Hardies  for  Blacksmiths 
are  made  of  crucible  steel  of  .65  to  .  75  per  cent,  carbon. 

Hobs  for  Dies 

are  made  of  crucible  steel  of  .90  to  i.oo  per  cent,  carbon, 
when  they  are  to  be  used  for  cutting  a  full  thread  in  a 
die.  If  they  are  to  be  used  for  sizing  only,  a  steel 
containing  1.20  to  1.25  may  be  used,  as  it  will  hold  its 
size  and  form  longer  than  if  made  of  steel  containing 
less  carbon. 

Jaws  for  Bench  Vises 

are  made  from  crucible  steel  of  .80  to  .90  per  cent, 
carbon.  Open  hearth  steel  is,  however,  extensively 
used  for  this  purpose. 

Jaws  for  Chucks 

are  strongest  if  made  of  crucible  steel  containing  .85 
to  1.00  per  cent,  carbon,  although  many  times  they  are 
made  from  a  good  quality  open  hearth  steel. 

Jaws  for  Cutting  Pliers 

are  made  from  crucible  steel  containing  i.io  to  1.25 
per  cent,  carbon.  When  they  are  to  be  used  for  cutting 
piano  or  other  hard  wire,  they  are  made  from  steel 
containing  1.40  to  1.50  per  cent,  carbon. 

291 


Jaws  for  Gripping 

work  in  various  fixtures  are  made  from  crucible  steel 
of  .  80  to  .  90  per  cent,  carbon. 

Jaws  for  Pipe  Machines 

are  made  from  crucible  steel  containing  i.oo  to  1.20 
per  cent,  carbon. 

Jaws  for  Screw  Threading  Dies, 

having  inserted  jaws  or  blades,  are  made  of  crucible 
steel  of  1.00  to  1.20  per  cent,  carbon. 

Jaws  for  Wire  Pullers 

are  made  from  i.oo  to  1.20  per  cent,  carbon  crucible 
steel. 

Knife  Blades. 

When  crucible  steel  is  used,  a  stock  containing  .9 
to  I.oo  per  cent,  carbon  is  selected. 

Knife    Blades, 

to  be  used  for  whittling  and  general  wood- working,  are 
made  from  i.io  to  1.25  per  cent,  carbon  crucible  steel. 

Knives — Draw  Knives 

are  made  from  crucible  steel  of  1.20  to  1.25  per  cent, 
carbon.  Many  times,  however,  they  are  made  of  open 
hearth  steel. 

Lathe  Tools 

for  ordinary  work  are  made  of  crucible  steel  containing 
1.25  per  cent,  carbon.  For  turning  hard  metals  or 
running  at  high  rate  of  speed,  use  steel  containing 
1.40  to  1.60  per  cent,  carbon. 


Lathe  Tools. 

For  turning  chilled  iron,  a  high  carbon  alloy  steel 
works  better  than  a  straight  carbon  steel. 

When  it  is  desirable  to  run  at  very  high  speeds, 
use  a  self -hardening  steel. 

Machinery  Crucible  Steel 
contains  .55  to  .65  per  cent,  carbon. 

Mandrels. 

Custom  differs  in  various  shops.  Some  mechanics 
consider  it  best  practice  to  make  mandrels  up  to  and 
including  i  inch  of  crucible  steel,  and  for  sizes  above  i 
inch  advocate  the  use  of  machine  steel,  case  hardened. 
Others  claim  best  results  from  crucible  tool  steel  for 
all  sizes.  Mandrels,  however,  do  not  require  a  steel 
containing  as  high  a  percentage  of  carbon  as  cutting 
tools.  Small  mandrels  give  good  satisfaction  when 
made  from  steel  of  from  i.oo  to  i.io  carbon,  larger 
sizes  made  of  steel  containing  .80  to  i.oo  per  cent. 

When  mandrels  are  hardened  by  the  process  known 
as  Pack  Hardening,  a  steel  containing  .75  to  .90  per 
cent,  will  give  excellent  results. 

Mowers. 

Lawn  mower  knives,  .90  to  i.oo  per  cent,  crucible 
steel,  although  in  many  instances  they  are  made  from 
open  hearth  steel. 

Planer  Tools  for  Stone, 
•75  to  .90  per  cent,  carbon  crucible  steel. 

Planer  Tools  for  Wood-working 
machinery  are  made  of  crucible  steel  containing  from 
I.IO  to  1.25  per  cent,  carbon. 

293 


Planer  Tools. 

If  the  tools  are  large  and  the  metal  to  be  machined 
is  comparatively  soft,  crucible  steel  containing  1.25 
works  nicely.  If,  however,  high  speeds  are  desired  or 
the  metal  to  be  cut  is  hard,  a  steel  containing  1.40 
to  1.50  per  cent,  carbon  gives  better  results,  provided 
care  is  exercised  in  heating  for  forging  and  hardening. 
If  the  stock  to  be  cut  is  extra  hard  or  it  is  desirable  to 
run  at  speeds  higher  than  is  practical  when  using  tools 
made  from  carbon  steels,  it  is  advisable  to  get  a  reliable 
self -hardening  steel. 

Punches  for  Hot  Trimming, 

.  85  to  1 .  00  per  cent,  carbon  crucible  steel.  Some  mechan- 
ics claim  as  good  results  if  the  punch  is  made  of  open 
hearth  steel  of  .  60  to  .  80  per  cent,  carbon,  while  others 
make  both  punch  and  die  of  open  hearth  steel.  These 
tools  may  be  hardened  in  the  ordinary  manner  or  they 
may  be  hardened  according  to  directions  for  hardening 
tools  made  of  machine  steel. 

Punches  for  Blanking  Work 

in  punch  press.  The  percentage  of  carbon  desirable 
depends  on  the  stock  to  be  cut  and  the  skill  of  the 
operators  doing  the  hardening  If  crucible  steel  is  used, 
a  range  of  .90  to  1.25  per  cent,  carbon  is  allowable,  de- 
pending on  the  character  of  the  work.  Many  times, 
however,  such  punches,  if  of  a  shape  and  size  that  in- 
sures strength,  are  made  of  .  40  to  .  80  per  cent,  carbon 
open  hearth  steel,  and  hardened  as  explained  under 
Making  Tools  of  Machine  Steel. 

Punches  for  Blacksmiths 
should  be  .  80  to  .  90  per  cent,  carbon  crucible  steel. 

294 


Punches  for  Railroad  Track  Work, 
about  .85  per  cent,  carbon  crucible  cast  steel  is  advis- 
able. 

Reamers. 
Small  reamers,  which  are  to  be  used  continuously, 
should  be  made  from  crucible  steel  of  1.25  to  1.50  per 
cent,  carbon.  When  they  are  to  resist  great  strain, 
steel  of  1. 00  to  1.25  per  cent,  may  be  used.  Excellent 
results  will  follow  if  steel  containing  .90  to  i.io  per 
cent,  carbon  is  used,  and  the  reamer  hardened  by  the 
method  described  under  Pack  Hardening.  This  is  es- 
pecially true  if  the  reamer  is  long  or  slender,  or  of  a 
shape  that  betokens  trouble  when  it  is  hardened. 

Saws  (Circular)  for  Wood, 
about  .80  to  .90  per  cent,  crucible  steel. 

Saws  for  Cutting  Steel 
are  made  from  1.25  to  1.50  per  cent,  crucible  steel. 

Scrapers  for  Scraping  Surfaces, 
1,50   carbon   crucible  steel.     Although  many  scraper 
hands  claim  best  results  from  using  a  high  carbon  alloy 
steel. 

Screw-Drivers, 
small,  .90  to  1. 00  per  cent,  crucible  steel;  large,  .65  to 
.80  per  cent. 

Stamps  for  Stamping  Steel, 
1.25  to  1.50  per  cent,  carbon  crucible  steel. 

Shafts  for  High  Speed  Machinery 
are  many  times  made  from  crucible  steel,  containing 
.65  per  cent,  carbon. 

Spindle  Steel, 
same  as  shafts. 

295 


Springs  for  Ordinary   Purposes 

are  made  from  i.oo  to  i.io  per  cent,  carbon  crucible 
steel.  For  many  purposes,  an  open  hearth  steel  is  used 
with  satisfactory  results. 

Springs  for  Locomotives 

are  made  by  some  manufacturers  of  crucible  steel  con- 
taining .90  to  1. 10  per  cent,  carbon,  and  by  others  of  a 
steel  containing  .80  to  .90  per  cent.,  while  in  many 
cases  very  satisfactory  results  follow  if  open  hearth 
steel,  made  especially  for  the  purpose,  is  used. 

Springs    for    Carriages 

are  made  from  crucible  steel  containing  .80  to  .90  per 
cent,  carbon,  but  many  more  springs  of  this  character 
are  made  from  open  hearth  and  Bessemer  stock  than 
from  crucible,  because  it  answers  the  purpose  and  is 
much  cheaper. 

Taps 

are  made  of  crucible  steel  containing  i.io  to  1.25  per 
cent,  carbon  in  many  shops,  while  others  claim  better 
results  from  steel  containing  1.25  to  1.40  per  cent. 

Taps  for  Tapping  Nuts, 

generally  called  machine  taps,  give  best  results  if  made 
from  steel  containing  i.oo  to  i.io  per  cent,  carbon. 


196 


Causes  of  Trouble, 


CO 

While  most  of  the  causes  of  trouble  when  steel  is 
hardened  have  been  considered  under  the  various 
topics  presented,  it  has  seemed  wise  to  group  together 
the  more  common  causes,  in  order  that  they  may  be 
referred  to  more  readily  by  the  reader. 

Uneven    Heats. 

Probably  the  most  common  cause  of  trouble  is  un- 
even heating  of  the  piece  in  forging,  annealing  or 
hardening.  As  a  consequence,  violent  strains  are  set 
up  which  cause  the  piece  to  crack  or,  in  the  case  of 
heavy  pieces,  to  burst.  The  different  parts  of  the  piece 
being  unevenly  heated,  must,  when  cooled,  contract 
unevenly;  and  when  two  portions  of  a  piece  adjoining 
each  other  attempt  to  contract  unevenly — that  is,  one 
contracting  more  or  faster  than  the  other — and  both 
being  rigid  to  an  extent  that  makes  it  impossible  for 
them  to  yield  one  to  the  other,  there  must  be  a  separa- 
tion at  the  point  where  the  uneven  temperature  occurs. 

High   Heats. 

A  very  common. cause  of  trouble  consists  in  heat- 
ing steel  too  hot  for  the  purpose.  High  heats  open  the 
pores  of  the  steel,  making  the  grain  coarse  and  causing 
the  steel  to  be  weak.     When  the  piece  is  broken,  it  has 

497 


Too  rapid  heating. 

a  honeycomb  appearance — looks  full  of  holes,  so  to 
speak.  Now,  as  there  is  but  a  very  thin  layer  of  steel 
over  these  holes,  when  pressure  is  applied  the  surface 
over  the  holes  caves  in,  and  the  steel  is  unfitted  for 
doing  the  maximum  amount  of  work. 

Steel  which  has  been  overheated  may  be  restored 
— unless  the  heat  was  high  enough  to  burn  or  disinte- 
grate the  steel — by  reheating  carefully  to  the  refining 
heat  and  quenching ;  but  it  can  never  do  the  amount  of 
work  possible,  had  it  not  been  overheated.  Yet,  it  will 
be  much  better  than  if  left  in  the  condition  the  high 
heat  placed  it. 

Then  again,  high  heats  have  a  tendency  to  cause 
the  steel  to  crack  when  hardened.  This  is  especially 
true  if  the  piece  be  cylindrical  in  shape.  Cylindrically 
shaped  pieces  will  not  stand  the  amount  of  heat  that 
may  safely  be  given  a  piece  of  almost  any  other  shape 
without  cracking,  although  the  effect  on  the  grain  and 
the  ability  of  the  steel  to  stand  up  and  do  the  maximum 
amount  of  work  possible  would  be  the  same  in  any  case, 
regardless  of  the  form  of  th  e  piece  or  the  method  of 
applying  the  heat. 

Too    Rapid   Heating. 

While  it  is  advisable  to  heat  steel  as  rapidly  as 
possible  consistent  with  good  results,  it  should  not  be 
heated  too  rapidly,  as  corners  and  edges  will  become 
overheated  before  the  balance  of  the  article  has  reached 
the  proper  heat ;  and  even  if  they  are  allowed  to  cool 
down  to  the  proper  heat  (apparently),  the  grain  has 
been  opened  at  these  portions,  and  violent  strains  are 
set  up.  This  is  one  of  the  places  where  experience 
seems  to  be  the  only  guide  and  where  the  instructor 

298 


Fire  cracks — how  to  avoid. 

can  only  give  suggestions,   wliicli  should  be  heeded 
and  worked  out  by  each  hardener. 

Heating   Too   Slowly. 

In  attempting  to  avoid  heating  too  rapidly,  do  not 
go  to  the  opposite  extreme  and  allow  the  steel  to 
**soak"  in  the  fire,  or  soft  surfaces  will  result,  and  the 
steel  is  not  as  good  as  if  heated  properly. 

Fire   Cracks. 

There  are  a  number  of  causes  for  steel  cracking  in 
the  fire.  Among  the  more  common  are,  first,  the  cold 
air  from  the  blast,  if  the  work  is  heated  in  a  black- 
smith's forge.  Then  again,  it  may  be  heated  in  a  gas 
flame  having  an  air  blast.  The  air  may  be  turned  on 
too  much,  resulting  in  cold  air  jets  striking  the  heated 
steel.  If  a  charcoal  fire  is  used,  it  is  the  custom  of 
some  hardeners  to  throw  cold  water  on  the  fire.  Now, 
if  the  steel  is  red-hot,  the  water  has  a  tendency  to  cause 
it  to  crack  in  the  same  manner  as  if  the  air  from  the 
blast  came  in  contact  with  it. 

Large  articles  plunged  in  a  crucible  of  red-hot 
lead,  cyanide  of  potassium,  or  any  substance  where  they 
are  exposed  to  violent  heats,  are  very  liable  to  crack, 
especially  if  there  are  heavy  and  light  portions  adjoining 
each  other.  The  unequal  expansion  tears  the  steel 
apart  at  the  point  where  the  unequally  heated  portions 
adjoin  each  other.  This  may  be  avoided  by  heating 
the  articles  nearly  to  a  red  in  some  form  of  fire  where 
it  would  heat  more  slowly,  then  plunge  in  the  lead  to 
bring  to  the  desired  heat ;  or,  the  article  may  be  im- 
mersed in  the  red-hot  contents  of  the  crucible,  left  for 
a  moment  and  withdrawn,  immersed  again,  leaving  a 

299 


Improper  forging. 

trifle  longer,    and   so   continue  until  it    reaches    the 
desired  heat. 

If  a  piece  of  steel  is  immersed  in  a  crucible  of  red- 
hot  lead  or  similar  material  for  a  certain  distance  so 
that  part  of  the  piece  is  out  of  the  red-hot  material,  it 
should  be  moved  up  and  down  in  the  molten  mass,  or 
the  part  below  the  surface  will  expand  more  rapidly 
than  the  adjoining  metal.  If  the  article  were  im- 
mersed and  withdrawn,  repeating  this  operation  until 
the  desired  result  is  obtained,  the  heat  being  applied 
gradually,  the  expansion  is  more  uniform,  and  the  heat 
is  imparted  to  the  adjoining  stock  so  it  can  yield  to  an 
extent  that  does  away  with  any  tendency  to  crack. 

Cold   Baths. 

Extremely  cold  baths  are  the  cause  of  a  great  deal 
of  trouble  when  pieces  of  irregular  contour  are  harden- 
ed. It  is  nearly  always  advisable,  when  hardening 
articles  made  of  high  carbon  steel,  to  warm  the  con- 
tents of  the  bath  somewhat.  Many  hardeners  claim 
that  oil  heated  to  a  temperature  of  loo  degrees  to  120 
degrees  will  harden  steel  harder  than  if  it  were  ex- 
tremely cold.     It  will  certainly  cause  it  to  be  tougher. 

Improper    Forging. 

This  is  the  cause  of  a  great  amount  of  trouble 
when  steel  is  hardened.  While  the  writer  claims  best 
results  from  steel  properly  forged,  he  is  aware  that 
much  better  results  are  obtained  from  steel  machined 
to  shape  than  if  the  articles  were  heated  or  hammered 
in  any  but  a  proper  manner. 

Steel  to  be  made  into  tools  whose  cutting  edges 
are  on  or  near  the  end  should  not  be  nicked  with. a  chisel 

300 


A  few  more  don*ts. 

and  broken,  as  the  portions  at  the  end  are  rendered 
unfit  for  cutting  purposes. 

Do  not  straighten  steel  that  is  to  be  hardened 
without  heating  it  red-hot. 

Do  not  attempt  to  harden  a  tool  of  irregular  shape 
unless  it  has  been  annealed  after  blocking  out  to  some- 
where near  to  shape. 

Do  not  take  it  for  granted  that  because  you  have 
held  a  piece  of  steel  in  the  fire  and  stuck  it  into  water, 
it  is  necessarily  hard.  Try  it  with  a  sharp  file  before 
brightening  the  surface  preparatory  to  drawing  the 
temper,  as  much  valuable  time  may  be  saved  if  the 
piece  should  prove  not  to  have  hardened. 

When  you  get  a  piece  of  steel  that  you  are  in  doubt 
about,  it  is  advisable  to  cut  a  small  piece  of  it  from  the 
bar  and  harden  it,  noticing  the  amount  of  heat  neces- 
sary to  produce  desired  results.  If  this  is  not  done, 
trouble  may  follow  when  the  article  is  hardened.  It  is 
better  to  experiment  with  a  small  piece  of  steel  than 
with  a  costly  tool. 

Do  not  use  any  but  chemically  pure  lead  in  a  crucible 
intended  for  heating  tools,  or  you  will  not  get  as  good 
results  as  you  might  otherwise  have. 

Do  not  think  that  because  the  surface  of  red-hot 
lead  appears  to  be  at  about  the  proper  heat,  that  the 
contents  nearer  the  bottom  of  the  crucible  are  neces- 
sarily of  the  same  temperature;  because,  generally 
speaking,  the  deeper  you  place  a  piece  of  steel  in  the 
contents  of  the  crucible  the  hotter  it  becomes.  Being 
ignorant  of  this  fact,  workmen  spoil  many  valuable 
articles,  and  then  think  the  lead  has  an  injurious  effect 
on  the  steel,  not  knowing  that  it  is  the  amount  of  heat 
given  rather  than  the  method  used  in  applying  it  that 

301 


Things  to  remember. 

caused  the  trouble.  Impure  lead  will  injure  the  sur- 
face of  the  steel,  but  will  not  alter  the  appearance  of 
the  grain  if  the  temperature  is  right. 

Remember  that  steel  heated  for  annealing  should 
not  be  subjected  to  heat  for  a  longer  period  of  time 
than  is  necessary  to  produce  a  7iniform  heat  of  the  de- 
sired temperature.  Steel  overannealed  does  not  work 
as  well  in  the  various  operations  of  machining,  neither 
will  it  harden  and  temper  as  satisfactorily  as  though 
properly  treated. 

Remember  that  heating  is  a  process  of  softening 
steel,  and  cooling  is  a  hardening  process.  The  slower 
the  process  of  cooling  is  carried  on  the  softer  the  steel 
will  be;  consequently,  it  is  never  advisable  to  place 
red-hot  steel  that  needs  softening  in  cold  or  damp  lime 
or  ashes. 

Always  use  a  clean  fire.  Dirty  slack  fires  are  a 
source  of  a  great  amount  of  trouble,  as  they  cause  the 
surface  of  the  steel  to  be  covered  with  a  sulphurous 
oxide. 

A  fire  of  new  coals  should  be  used  (when  using  a 
charcoal  fire)  for  heating  steel.  Dead  coals  require 
more  blast  than  is  good  for  the  steel. 

Ten  pieces  of  steel  are  cracked  as  a  result  of 
uneven  heating  to  every  one  that  is  the  result  of  a 
defect  in  the  steel. 

Do  not  think  that  because  the  surface  of  a  hardened 
piece  of  steel  is  not  scaled  that  it  is  not  overheated. 
Every  degree  of  heat  given  it  above  that  necessary  to 
produce  the  desired  result  unfits  the  steel  for  doing  the 
maximum  amount  of  work  possible  for  it  to  do. 

Always  harden  on  an  ascending  heat.  Never  heat 
a  little  too  hot  and  allow  to  cool  down  to  the /r^<?r  heat, 

302 


About  carelessness. 

as  the  grain  of  steel  remains  in  the  condition  the  last 
heat  leaves  it.  To  refine,  it  is  necessary  to  allow  it  to 
cool  off,  and  then  reheat  to  the  proper  hardening  heat. 

It  often  happens  that  the  hardener  is  blamed  for 
things  he  is  entirely  innocent  of.  A  man  in  this  posi- 
tion is  liable  to  have  enough  spoiled  work  to  account 
for  that  is  the  result  of  his  own  carelessness  or  ignor- 
ance without  being  obliged  to  shoulder  the  short- 
comings of  others.  It  may  be  that  some  careless 
blacksmith  has  forged  a  tool  at  heats  which  unfitted  the 
steel  for  the  purpose  for  which  it  was  intended.  He 
may  have  heated  the  steel  too  hot,  and  opened  the 
grain,  causing  brittleness,  or  he  may  have  had  uneven 
heats  when  he  was  forging,  thus  setting  up  internal 
strains  which  would  cause  the  steel  to  crack  when 
hardened.  Then  again,  the  tool  maker  may  have  at- 
tempted to  straighten  the  piece  without  heating  it  red- 
hot,  in  which  case  it  is  almost  sure  to  spring  when 
hardened.  Or,  in  the  case  of  a  long  reamer  or  tap,  the 
flutes  may  have  been  milled  with  a  dull  cutter,  which 
would,  of  course,  get  duller  the  longer  it  was  used,  with 
the  result  that  by  the  time  the  last  flute  was  milled  the 
tool  would  have  been  stretched  very  materially.  This 
is  especially  true  on  the  side  where  the  last  cuts  were 
taken,  as  the  cutter  would  be  duller  than  when  the 
flutes  on  the  opposite  side  were  milled,  and  the  uneven 
stretching  of  the  stock  would,  of  course,  spring  the 
reamer. 

Another  difficulty  would  also  present  itself.  The 
dull  cutter  would  glaze  the  surface  of  the  tooth  that 
came  in  contact  with  the  dulled  portion  of  the  mill,  and 
any  surface  of  steel  which  is  glazed,  whether  it  be  from 
the  action  of  cutting  tools  or  grinding  wheels,  will  not 

303 


The  effect  of  not  paying  attention. 

harden  in  a  satisfactory  manner.  This  difficulty  is 
more  pronounced  in  the  case  of  a  piece  glazed  from  the 
action  of  grinding-  wheels.  While  a  glazed  surface 
might  not  be  considered  objectionable,  if  it  was  to  be 
ground  away  after  hardening,  yet  it  is  not  always  con- 
sidered advisable  to  grind  the  cutting  faces  of  reamer 
and  milling  machine  cutter  teeth.     There  is  no  good 


.The  Derry  Collard  Co. 

Figure  156.     The  spring  of  a  mandrel. 

excuse  for  using  dull  tools  when  machining  steel.  Not 
only  does  it  lead  to  trouble  when  the  pieces  are  hard- 
ened, but  it  is  a  means  of  wearing  the  tools  out  much 
faster  than  if  they  were  kept  sharp.  Neither  can  as 
much  nor  as  good  work  be  done  with  dull  tools. 

It  is  often  the  case  that  a  careless  workman  will 
mill  the  flutes  in  a  long  reamer,  tap,  or  similar  tool, 
without  supporting  the  work  properly.  In  this  way  the 
tool  is  sprung,  first  one  way,  then  the  other.  This  not 
only  results  in  a  crooked  tool,  but  there  is  no  knowing 
where  it  may  go  when  hardened.  Many  times  hard- 
ened pieces  are  sprung  by  heating  when  grinding. 
This  is  especially  true  with  pieces  that  may  have  sprung 
when  hardened.  Take,  for  instance,  a  long  mandrel 
which  may  have  gone  in  the  direction  shown  in  Fig.  156. 
Now,  if  this  mandrel  were  placed  in  a  grinder  and 
ground  in  a  manner  that  caused  it  to  become  heated  on 
the  side  that  is  already  curved  out,  as  shown  in  cut,  it 
would  spring  still  more. 

Many  times  thin,  flat  pieces  are  sprung  from  the 

304 


What  caused  the  cracks. 

expansion  of  one  side  when  ground  in  a  surface 
grinder.  The  side  which  comes  in  contact  with  the 
wheel  becomes  heated,  while  the  opposite  side,  from 
contact  with  a  mass  of  cold  iron — the  table — remains 
cool.  The  side  which  heats  must  expand,  with  the  re- 
sult that  the  piece  is  curved  in  the  direction  of  the  heated 
side. 

When  flat  pieces  which  are  hardened  are  ground 
with  a  glazed  wheel  or  one  too  fine  for  the  purpose, 
they  are  very  liable  to  crack,  commencing  at  the  edge 
or  end  where  the  wheel  leaves  the  work.  Fig.  157  re- 
presents a  rectangular  gauge  which  cracked  as  a  result 


-@ 


The  Derry  Collard  Co. 


Figure   157.      Cracked  gauge. 


of  grinding.  The  fault  was  laid  at  the  hardener's  door, 
and  he,  poor  fellow,  was  doing  his  best  to  harden  the 
gauges  in  a  satisfactory  manner,  so  he  said  the  steel 
was  no  good.  An  investigation  showed  the  cracks  to  be 
from  the  end  where  the  wheel  left  the  gauge  when 
grinding  in  the  surface  grinder.  The  vise  which  held 
the  piece  was  turned  one-quarter  way  around,  and  it 
was  found  that  the  cracks  were  from  one  side^  instead 
of  the  end  of  the  piece.  An  examination  of  the  wheel 
revealed  the  fact  that  it  was  too  fine  for  the  purpose, 
and  that  it  was  badly  glazed.     A  coarse  wheel,  free  from 


305 


Cracking  from  the  wrong  use  of  water. 


glaze,  was  substituted  and  the  gauges  were  found  to  be 
sound  after  grinding. 

Not  only  may  hardened  steel  be  sprung  and  cracked 
from  heat  generated  when  grinding,  but  it  may  also  be 
cracked  if  water  is  run  on  it,  unless  due  care  is  observed. 
If  the  operation  is  hurried  to  the  extent  that  it  becomes 
heated,  even  when  the  water  is  running  on  it,  the  water 
cools  the  piece,  which  is  instantly  heated  again  and 
then  cooled.  This  sudden  expansion  and  contraction 
causes  the  steel 
to  become 
cracked  in 
innumerable 
places,  these 
cracks  running 
in  all  directions.  - 
This  trouble 
may  occur  when 
grinding  pieces 
of  almost  any 
shape.  The 
cracks  may  oc- 
cur on  the  sur- 
face of  a  cylin- 
drical piece,  on  the  flats  of  a  square,  or  on  the  face  of 
an  article  being  ground.  Fig.  158  represents  a  disc 
whose  face  was  cracked,  as  represented,  when  ground, 
with  a  stream  of  water  running  on  the  work.  The  fault 
did  not  lay  in  using  water,  but  in  forcing  the  grinding 
faster  than  the  wheel  could  properly  cut  the  metal. 

These  few  facts  are  pointed  out,  because  it  often 
happens  that  when  these  troubles  arise,  the  party  doing 
the  hardening  is  blamed,  and  unless  he  is  sufficiently 

306 


Fig.  158.     Disc  cracked  from  being 
ground  too  rapidly. 


A  proper  emery  wheel  for  cutter  teeth. 

versed  in  the  action  of  emery  wheels  on  surfaces  of 
steel,  he  naturally  thinks  the  fault  is  either  in  the  steel 
or  in  his  method  of  treating  it. 

Very  often  milling  machine  cutter  teeth  are  soft- 
ened when  ground,  the  hardener  being  blamed  as  a  con- 
sequence. It  is  not  good  practice  to  use  a  very  fine 
wheel  when  grinding  tools  of  this  description,  neither 
should  too  hard  a  wheel  be  used.  Ordinarly  an  emery 
wheel  made  of  60  to  90  emery  will  be  found  about 
right,  and  be  sure  the  face  of  the  wheel  is  not  glazed. 
Should  it  become  glazed,  use  a  piece  of  emery  wheel 
somewhat  coarser  than  the  one  in  use  to  remove  the 
glaze.  This  also  makes  the  face  of  the  wheel  open, 
and  lessens  the  liability  of  heating. 

Many  times  the  writer  has  seen  workmen  using  a 
tool  ground  in  a  manner  that  made  it  impossible  for  it 
to  cut.  It  was  forced  into  the  stock,  and  broke  it  off. 
The  tool  could  not  stand  this  treatment,  and  gave  right 
out,  the  workman  in  the  meantime  saying  things  about 
the  hardener.  When  the  tool  was  properly  ground,  it 
worked  all  right. 

Some  mechanics  do  not  seem  to  realize  that  there 
is  a  proper  speed  to  run  stock  or  cutting  tools,  in  order 
to  get  desired  results.  As  a  consequence,  they  either 
run  them  much  too  fast,  with  the  result  the  tools  can 
not  stand  up,  or  they  are  afraid  they  will  exceed  the 
proper  speed,  and,  as  a  consequence,  do  not  produce 
anywhere  near  the  amount  of  work  they  might. 

When  cutting  a  key  way  or  spline  in  a  tool  that 
is  to  be  hardened,  the  tool  maker  should  avoid  sharp 
corners,  as  they  are  an  invitation  for  a  crack  when  the 
steel  is  rapidly  cooled  in  the  bath.  While  an  article 
having  sharp  corners  is  not  as  liable  to  crack  when 

307 


How  tools  are  weakened  by  grinding. 

hardened  by  the  process  termed  Pack  Hardening  as 
when  treated  in  the  ordinary  manner,  it  is  not  advisable 
to  in  any  way  weaken  a  tool,  or  give  it  an  invitation  to 
crack.  Consequently,  avoid  sharp  comers  as  far  as 
possible,  or  cuts  or  deep  scratches  that  tend  to  weaken 
the  article. 

A  milling  machine  cutter,  made  with  light,  weak 
teeth,  can  not  be  made  to  stand  up  when  in  use ;  the 
teeth  being  slender  and  weak,  break  like  pipe-stems. 
Cutters  with  teeth  of  this  description  require  greater 
care  when  hardening,  to  avoid  overheating.  Being 
slender,  they  spring  and  break.  Do  not  blame  the 
hardener  if  they  fail  to  give  s-atisfaction  when  in  use. 

Another  source  of  trouble  is  fine  teeth  in  milling 
cutters,  reamers,  and  similar  tools.  The  teeth,  being 
fine,  fill  with  chips,  and  in  the  case  of  milling  machine 
cutters,  the  oil  not  being  able  to  get  to  the  teeth,  can 
not  conduct  away  the  heat  generated,  which  has  the  ef- 
fect of  drawing  the  temper  to  a  degree  that  makes  it 
impracticable  to  use  them. 

A  short  time  ago  the  writer's  attention  was  called 
to  a  side  tool  for  use  in  an  engine  lathe.  The  tool  was 
made  from  a  well-known  brand  of  steel,  which  is  gen- 
erally considered  one  of  the  best  steels  on  the  market. 
It  was  claimed  that  the  tool  could  not  be  made  to  keep 
an  edge  on  a  mild  grade  of  machine  steel  running  at  a 
periphery  speed  of  30  feet  per  minute,  taking  a  fair  cut. 

An  examination  of  the  tool  revealed  the  fact  that 
it  was  ground  in  such  a  manner  that  the  cutting  edge 
had  no  backing.  It  might  possibly  have  stood  up 
if  the  material  being  machined  had  been  wood  in- 
stead of  steel.  Because  the  tool  would  not  stand, 
the  hardener  was  considered  as  being  to  blame.    When 


Why  reamers,  broaches,  etc.,  break. 

properly  ground,    it   stood   up    all  right    without   re- 
hardening. 

Milling  machine  cutter  teeth  are  many  times  ground 
with  too  great  an  angle,  and  the  cutting  edge,  not  having 
backing,  gives  way.  Or  it  may  not  be  given  as  much 
clearance  as  it  should  have.  As  a  consequence,  the  heel 
of  the  tooth  rubs,  and  the  friction  resulting  trom  this 
contact  of  the  heel  of  the  tooth  with  the  material  being 
machined  produces  heat,  which  softens  the  tooth.  It 
is  tried  with  a  file,  found  to  be  soft,  and  the  hardener 
is  blamed. 

Many  times  the  liquid  supplied  to  keep  cutting  tools 
cool,  and  to  lubricate  the  cutting  edges,  can  not  reach 
the  cutting  edges  of  the  tool.  As  a  consequence,  it 
becomes  heated  and  the  temper  drawn.  This  is  es- 
pecially liable  to  happen  to  tools  used  on  automatic 
screw  machine  work,  where  heavy  cuts  are  being  taken. 

Twist  drills,  used  in  drilling  very  deep  holes  in 
steel,  are  very  liable  to  receive  insufficient  lubrication, 
unless  supplied  with  oil  tubes,  because  the  oil  which 
is  fed  down  the  flute  is  forced  back  by  the  action  of  the 
chips  and  the  angle  of  the  flutes. 

Taps  are  allowed  to  become  clogged  with  chips,  and 
break ;  the  hardener  is  blamed,  because  the  tap,  it  is 
claimed,  is  too  hard.  Broaches  break  from  the  same 
cause,  and  the  trouble  is  placed  at  the  hardener's  door. 
Reamers  are  allowed  to  become  clogged,  the  cutting 
edge  chips  off,  and  it  is  said  the  steel  is  burnt. 

Cases  of  this  character  might  be  enumerated  by  the 
thousands,  but  it  is  needless.  The  tool  maker  should 
bear  in  mind  that  a  place  must  be  provided  for  the  chips 
made  when  a  tool  is  cutting,  or  roughly  machined  sur- 
faces or  broken  tools  (possibly  both)  must  follow. 

309 


Welding. 


G-<?=\  /=^ 


CO 

When  it  is  considered  necessary  to  join  two  pieces 
of  iron,  thus  making  them  one,  or  when  it  is  desirable 
to  join  the  two  ends  of  a  bar,  thereby  making  a  ring, 
it  is  accomplished  by  the  process  called  welding. 

This  is  of  inestimable  value  as  applied  to  the 
mechanic  arts.  Not  only  may  iron  be  welded  to  iron, 
but  steel  may  be  joined  to  steel  by  this  process.  Iron 
may  also  be  joined  to  steel. 

It  is  accomplished  by  heating  the  metal  to  a  tem- 
perature that  makes  the  surface  of  a  pasty  consistency, 
which  for  soft  steel  should  be  a  dark  white,  for  iron  a 
scintillating  white,  while  for  tool  steel  it  should  be  a 
bright  yellow.  The  formation  of  a  soft  pasty  layer  on 
the  surface  of  the  steel  is  an  absolute  necessity,  in  order 
to  effect  a  union  of  the  pieces  of  metal.  This  operation 
is  assisted  by  scattering  fusible  substances  on  the  sur- 
faces to  be  united,  as  these  protect  the  work  from 
oxidation.  These  substances  are  termed  /luxes. 
Among  those  most  commonly  used  are  borax,  clay, 
potash,  soda,  sand  and  sal  ammoniac.  Ordinary  red 
clay,  dried  and  powdered,  is  an  excellent  flux  for  use 
when  welding  steel,  and  is  one  of  the  cheapest  known. 
Borax  melted  and  powdered  is  called  the  best  of  known 
fluxes,    but  it  is   so   expensive  when  used  in  large 

31Q 


A  good  flux  for  welding. 


quantities,  that  its  use  is  confined  to  the  finest  tool 
steels  and  alloy  steels  where  it  is  not  possible  to  heat 
the  metal  as  hot  as  a  lower  grade  of  steel. 

A  very  good  flux,  whose  cost  is  about  one-half  that 
of  borax,  is  a  mineral  barite,  or  heavy  spar.  It  does 
not  fuse  as  readily  as  borax,  however,  but  forms  an  ex- 
cellent covering  for  the  heated  surface  of  the  steel.     It 

is  necessary  to  fur- 
nish this  coating  for 
the  surface  of  the 
steel,  in  order  to  pre- 
vent oxidation;  for 
if  any  portion  is 
oxidized,  no  matter 
how  small  the  por- 
tion may  be,  it  fur- 
nishes  a  starting 
point  for  a  break  or 


Figure  159.      First  operation  on  special 
swaging  die. 


fracture  when  the  piece  is  under  heavy  stress.  Al- 
though steel  may  be  welded,  it  is  a  job  to  be  avoided 
when  the  welded  piece  requires  hardening. 

Pieces  are  welded  and  afterwards  hardened  which 
remain  intact,  but  it  is  not  advisable  unless  the  weld  is 
to  be  made  by  a  smith  skilled  in  this  particular  branch 
of  the  business,  and  even  then  it  is  attended  with  vary- 
ing results. 

The  writer  was  at  one  time  connected  with  a 
manufacturing  concern  who  built  50  machines  for 
swaging  wire.  The  operation  of  reducing  the  diameter 
of  the  wire  was  accomplished  by  dies  known  as  swag- 
ing dies.  These  were  actuated  by  hammers  working 
inside  of  a  large  ring.  This  ring  was  made  of  tool 
steel,  and  in  order  to  save  expense,  it  was  considered 

311 


Why  the  piece  broke  at  the  weld. 


advisable  to  take  flat  steel  of  the  desired  size  to  allow 
for  finishing  all  over,  bend  in  the  form  of  a  ring  and 
weld  the  ends.  A  very  skillful  smith  was  given  the 
job,  but  when  finished  and  hardened,  the  rings  broke 
apart  at  the  weld.     When  broken  to  examine  the  grain, 

it  was  evident  that 
the  smith  had  used 
extreme  care,  yet 
a  small  portion  of 
the  welded  surface 
was  found  to  be 
oxidized ;  c  o  n  s  e  - 
quently,  it  could 
not  unite  at  that 
place,  and  a  rup- 
ture started  from 
that  point. 

The  method  of 
procedure  was 
changed,  stock 
sufficiently  large 
was  procured  and 
split,  as  shown  in  Fig.  159.  It  was  then  opened  until 
it  resembled  Fig.  160,  and  was  afterward  hammered 
to  shape.  Before  shaping  by  hammering,  however, 
the  sharp  comers  were  removed  by  means  of  a  chisel. 
After  machining  to  the  desired  size  to  allow  for  grind- 
ing, they  were  hardened  as  described  under  Harden- 
ing Large  Rings,  with  the  result  that  not  one  was 
lost. 

While  steel  can  be  welded  if  great  care  is  used,  it 
is  very  apt  to  result  disastrously  if  the  steel  is  to  be 
hardened.      Not  only  has  this  been  the  writer's  ex- 


The  De/ry  CoUard  Co, 

Figure  i6o.      The  special  swaging  die  finished. 


31a 


Substitute  for  borax. 

perience,  but  it  seems  to  be  the  experience  of  most 
practical  writers  on  the  subject. 


Other  Things, 


CO 

Substitute   for  Borax. 

The  following  rule  for  preparing  a  substitute  for 
borax  for  use  in  welding  high  carbon  tool  steel  was 
given  the  writer  several  years  ago  by  a  blacksmith  who 
was  considered  as  an  expert  in  welding  steel.  He 
claimed  that  steel  could  be  welded  by  use  of  this  flux 
at  a  lower  temperature  than  is  required  with  borax : 

Copperas 2  ounces. 

Common  Salt 6       *' 

Saltpetre i  ounce. 

Black  Oxide  Manganese,  i       *  * 

Prussiate  of  Potash i       ** 

All  pulverized  and  mixed  with  3  lbs.  good  welding 
sand. 

Charred    Leather. 

While  it  is  possible  to  purchase  charred  leather  of 
a  desirable  quality,  so  much  depends  on  the  condition 
of  this  article  that  it  is  always  advisable  to  prepare  it 
in  the  shop  where  it  is  used,  if  possible. 

Use  heavy  leather,  as  scraps  left  when  shoe  soles 
are  punched.     Never  use  light  leather,  as  there  is  little 

313 


Charred  bone  for  colors. 

goodness  in  it  after  charring.  The  very  best  article  for 
the  purpose  can  be  procured  from  shoe  shops. 

To  char  the  leather,  fill  one  or  more  hardening 
boxes  with  small  pieces,  place  the  cover  in  position  and 
seal  with  fire-clay.  Place  in  the  furnace,  leaving  it 
just  long  enough  to  char  sufficiently,  so  it  can  be  pounded 
fine.  Do  not  expose  it  to  the  action  of  heat  long  enough 
to  destroy  the  '•'•  goodness''  of  the  leather. 

A  very  satisfactory  method  is  to  fill  boxes,  9x9x36 
inches,  with  the  leather  scraps,  sealing  the  covers  as 
described,  and  placing  them  in  the  furnace  at  night 
after  the  work  has  been  withdrawn.  The  remnant  of 
fire  and  the  heat  of  the  furnace  are  sufficient  to  char  the 
leather  during  the  night.  As  previously  stated,  do  not 
overchar.  It  should  be  exposed  to  the  action  of  heat 
only  long  enough  to  break  in  pieces  readily  when 
pounded.  If  smaller  boxes  are  used,  it  is  not  advisable 
to  leave  in  the  furnace  over  night.  They  must  be 
watched,  and  taken  out  when  the  leather  is  charred 
sufficiently. 

Charred  Bone   for   Colors. 

It  is  necessary,  in  order  to  obtain  nice  colors,  that 
the  work  be  polished  and  absolutely  clean ;  unpolished 
surfaces  will  not  color.  Grease  also  prevents  the  ob- 
taining of  satisfactory  work. 

Pack  the  work  in  boxes  as  previously  described, 
except  that  charred  bone  is  used  as  packing  material. 
When  it  has  run  the  proper  length  of  time,  remove  the 
box  from  the  furnace,  and  dump  into  a  tank  of  water 
having  a  jet  coming  up  from  the  bottom.  Better  colors 
are  obtained  if  a  bath  is  used  having  an  air  pump  con- 

314 


How  to  char  bone. 

nected  with  the  inlet  pipe,  as  illustrated  in  Fig.  134. 
This  shows  an  easy  way  of  putting  in  an  air  pipe, 
connected  with  inlet  water  pipe.  Soft  water  in  the 
bath  gives  much  better  results  than  hard,  although 
very  satisfactory  results  may  be  obtained  with  hard 
water  if  the  air  pipe  is  connected  as  described. 
When  hardening  for  colors  by  the  method  under  con- 
sideration, it  is  essential  that  the  box  be  held  very  close 
to  the  top  of  the  water  when  dumping  the  work ;  the 
box  should  be  inverted  quickly,  to  prevent  the  air 
striking  the  work  before  it  reaches  the  water.  If  the 
air  comes  in  contact  with  the  metal,  the  surface  as- 
sumes a  blue-black  color.  This  is  sometimes  desirable, 
but  not  in  connection  with  work  packed  especially  for 
hardening  for  colors. 

When  the  work  is  cold,  it  may  be  removed  from  the 
bath  and  boiled  in  clean  water.  Dry  in  sawdust,  and 
oil  the  surface  either  with  sperm  oil  or  vaseline.  This 
has  the  effect  of  making  the  colors  more  prominent, 
and  it  will  also  keep  the  steel  from  tarnishing  or  rusting. 

To   Char  the   Bone. 

It  is  sometimes  considered  desirable  to  use  bone 
rather  than  leather,  and  it  is  thought  that  the  expended 
article  would  not  give  the  necessary  hardness.  Yet  it 
may  be  necessary  that  the  articles  be  tough.  This  may 
be  accomplished  by  taking  raw  bone,  filling  a  small 
hardening  box  with  it,  placing  the  cover  in  position, 
and  sealing  with  fire-clay.  When  the  day's  work  of 
hardening  is  taken  from  the  furnace,  the  box  may  be 
placed  in  it,  the  door  shut,  the  fire  extinguished,  and 
the  box  left  until  morning.     If  the  furnace   is   one 

315 


How  to  preserve  the  bone. 

having  light  walls,  that  would  lose  their  heat  rapidly,  it 
would  be  found  necessary  to  apply  the  heat  for  a  time. 
The  bone  will  be  found  charred  when  the  box  is  opened. 
Care  should  be  observed  that  the  charring  is  not  over- 
done^  however. 

Charred  bone  may  be  used  as  packing  material 
either  alone  or  with  an  equal  quantity  (in  volume)  of 
granulated  wood  charcoal. 

Preserving  the   Bone. 

When  the  hardened  articles  are  removed  from  the 
bath,  the  water  may  be  drawn  off,  and  the  packing  ma- 
terial taken  out  and  dried.  This  may  be  done  by 
placing  it  on  top  of  the  hardening  furnace,  if  that  be  of 
sufficient  size ;  if  not,  it  may  be  spread  out  thinly  and 
allowed  to  dry.  This  is  the  expended  bone  previously 
mentioned. 

Expended  bone  may  be  used  for  packing  certain 
classes  of  work  in,  or  it  may  be  mixed  with  an  equal 
quantity  of  granulated  raw  bone  and  used  the  same  as 
raw  bone.  Or  it  may  be  used  for  packing  machine 
steel  forgings  or  small  articles  of  cast  iron  for  an- 
nealing. 


316 


An  Index  to  Contents 


CO 


Action  of  charcoal  on  steel 36 

Cyanide 10 

Aging  of  gauges 196 

Steel 241 

Agitated  baths 90-91-93 

Air  annealing 71 

Air  blast  for  cooling 230 

Should  not  strike  steel 35-63 

Air  blasts  cause  cracks 299-302 

Air  hardening  steel 278 

Annealing 23 1 

Air  jet  in  case  hardening 233 

Alloy  steels 277 

Anneal  at  uniform  heat 84 

Annealing 271 

After  blocking  out 301 

Between  boards 73 

Methods  of 71 

Roughing  out 78 

Annealing  in  ashes 72 

Cold  water 73 

Crucibles 97 

Furnace — danger  of 74-75 

Gas  furnace 74-75 

Iron  boxes 75-76-77 

Lime 72 

Machinery  steel 81 

Object  of 71 

Self-hardening  steel 28 1 

Sheet  steel 270 

Wrong  way 81 

Arbors  and  mandrels 219-220 

317 


Arbors  for  saws 236 

Arbors — taper 187 

Appliances  for  case  hardening .242 

Ashes  for  annealing 72 

Attempting  the  impossible 127 

Augers 287 

Axes 287 

Axles — case  hardening  of 246 

Balls — case  hardening  of 242 

Barrel  for  hardening  bath 256-257 

Barrels  for  guns 287 

Baskets  for  hardening Ill 

Bath  for  case  hardening  small  pieces 229 

Cooling  mandrels,  etc 191 

Grooved  rolls 194 

Hardening  taps 157-158-160 

Springs 86 

Toughening 87 

Bath  of  oil  for  springs 263-264 

Baths  for  case  hardening 254 

Baths  for  hardening. 

Brine 86-89 

Citric  acid 87 

Hardening 85-86-87-96 

Hardening  dies 133-135-136 

Heated 66-92 

Heat  for  best  work 156 

Lead 96 

Mercury 85 

Oil 86 

Oil  and  water 88 

Poisonous  baths 87 

Saltpeter 87 

Springs 260-261 

Sulphuric  acid  bath 87 

Water 86 

With  liquid  in  motion 90-91-93 

Bench  vises — jaws  for 29 1 

Bessemer  steel — case  hardening  of 238 

Hardening 1 1 1 

Not  good  for  tools 275 

^3.8 


Best  steel  for  mandrels  or  arbors 189 

Punches 142 

Bevel  gears  for  bicycles 235 

Bicycle  axles 246 

Chains 239 

Cones— hardening 202 

Crank  testing 82 

Parts— case  hardening 234 

Blacksmiths'  chisels 287-288 

Forge  for  hardening  dies 129-130 

Forge — heating  in 35 

Hammer 290 

Hardies 29 1 

Punches 294 

Blades  of  knives 290 

Blame — shifting  of 80 

Blaming  the  hardener 303 

Blanking  dies 214 

Blanking  press  dies 289 

Blanking  work  punches 294 

Blister  steel 276 

Blocking  out  work  for  annealing 78 

Blow  pipe  and  candle  for  tempering 162 

Blow  pipe  and  spirit  lamp 44-45 

Boiling  water  for  springs 265 

Bolt  dies 289 

Bone 223 

Black  for  case  hardening 223 

Cast  iron  in 316 

Charred 314-315 

Expended 316 

Packing  steel  in 316 

Preserving 316 

Should  never  be  used  in  pack  hardening 250 

Borax — substitute  for 313 

Boxes  for  heating  dies 132 

Pack  hardening 206-209 

Box  for  case  hardening 227-239 

Hardening  springs 263 

Heating  swaging  dies 224 

Brine  bath 86 

Brittleness 66 

319 


Brittleness — due  to  phosphorus * 63 

In  wood-working  tools 200 

Bunsen  burner 4445 

Burns  from  cyanide — caution 110 

Burnt  steel — restoring 298 

Bursting  from  internal  strains 65 

Cams  of  low  grade  steel 24 1 

Candle  and  blow  pipe  for  tempering 162 

Carbonaceous'paste 46 

Carbon  and  quality 22 

Best  for  various  tools 284 

Necessary  for  good  results 29 

Penetrates  iron 275 

Percentage  of 15-20-21-29-33 

Surface 63 

Careful  hammering ,  69 

Carelessness  303 

Careless  workmen 17 

Carriage  springs , 296 

Case  hardening 225 

Baths. 254 

Bicycle  parts 235 

Furnaces 253-254 

Gas  pipe 226 

Imitation  of Ill 

Machine  nuts 251 

Many  small  pieces 229 

Portion  of  piece 248 

To  leave  soft  places 249-250 

Cast  iron  bad  for  steel 206 

In  annealing 76-81 

Cast  steel 286 

Catch  pan  in  baths 229-256 

Causes  of  trouble 297 

Cautions  about  lead  bath 100 

Cemented  steel 275 

Centering  steel 23-24 

Centers  for  lathes 287 

Of  mandrels  or  arbors  should  be  hard 191 

Chain  blocks 239 

Chain  studs 247 

2^o 


Charcoal 232 

Action  of  on  steel 36 

Annealing 75-76-77 

Prevents  dross 101 

Charred  bone  for  colors 314 

Leather  for  annealing 85 

Leather  for  heating  dies 132 

Leather — making 313 

Leather  toughens  steel 239 

Charring  the  bone 315 

Cheapening  cost  of  production 8 

Cheap  steel 31 

Chilled  iron— steel  for 28 1-282 

Tools  for 293 

Chisels  for  cutting  steel 287 

Chisels  for  wood 287 

Chisel  temper 27 

Choosing  steel 28 

Chuck  jaws 29 1 

Cigars — effect  on  steel 87 

Circulation  of  water  necessary 256-257 

Citric  acid  bath 87 

Clay  for  filling  corners 176 

Clean  fires 302 

Clock  springs— hardening 260 

Coals  not  always  good 63 

Coke  for  high  carbon  steel 37 

Cold  air  blast  cracks  steel 35-63 

Baths  not  usually  advisable 1 14-300 

Bending  of  springs 269 

Causes  cracks 299 

Chisels 287-288 

Water  annealing 73 

Water  bad  for  springs 259 

Work 287-288 

Collars  to  prevent  case  hardening 251 

Color  blindness 11 

Coloring  gun  frames 109 

Colors  denote  temper 1 17-123 

For  springs 269 

In  case  hardening 233 

Obtained  with  cyanide 108 

321 


Colors  on  case  hardened  work 258 

On  malleable  iron Ill 

Reason  for 124-125 

Visible 117 

Cooling  case  hardened  work 234 

Deep  hole  in  die 94 

Device  for  gauges 196 

Dies  for  screw  cutting 151 

Flat  plates 179 

Grooved  rolls 193 

Gun  springs 182 

Half  round  reamers 163 

In  air  blast 280 

In  bath 14 

In  small  bath 94 

Jaws  of  hardening  device 181 

Milling  cutters 166 

Pieces  with  holes  near  edge 199 

Plate  mounted  on  springs 181 

Shank  mill 94 

Springs 262-263-264 

The  oil  bath 263-264 

Thin  pieces 245 

With  dirty  water 95 

Commercial  bars  vs.  hammering 70 

Common  error 279 

Compounds  for  hardening 88 

Cones  for  bicycles— hardening 202 

Considerations  in  hardening 127 

Continued  heating 84 

Continuous  or  agitated  baths 90-9 1-93 

Contraction  and  expansion 12-14 

Converted  steel 275 

Correcting  wrong  annealing 82 

Cost  of  production 8 

Testing  steel 33 

Counterbores 158-187-188 

Countersinking  too  deeply 187 

Covering  paste 46 

Cracking  in  lead  bath. 100 

Liability  of 271 

Of  hollow  articles 175 

322 


Cracking  of  round  pieces 62 

Cracks 14-35-298-299 

Cause  of 305 

Prevention  of 203-204 

Where  they  occur 100 

Crank  axles — hardening 235-246 

Critical  temperature 13 

Crucible  cast  steel 276 

Steel 286 

Crucibles — annealing 97 

Should  always  be  emptied 101 

Used  for  lead  baths 97 

Crushing  grain  in  hammering 69-70 

Cutters  for  milling  machine 288 

Glass 288 

Pipe  cutting 288 

Cutting  pliers 291 

Point  of  tools 7 

Tools— hardening 86-87 

Tools  of  machine  steel 241-243-272-274 

Cyanide — action  of 106 

Bath  best  for  cutting  tools 105 

Bath  for  watch  springs 267 

Coloring  with 108 

Hardening  furnace 106 

Hardens  surface 107 

Heated  in  open  forge 50 

Heating  bath — advantage  of 46-108 

Of  potassium  a  poison 107 

Of  potassium  bath 105 

Of  potassium  for  case  hardening 227 

Of  potassium  furnace 51-52 

Should  be  chemically  pure 106 

Solution  prevents  lead  sticking 98-103 

Dampers 39-40 

Danger  from  small  fire 190 

Cracking  removed 138-139 

In  steel  welds 311 

Of  cast  iron  in  annealing 76-81 

Overheating  in  annealing 74-75-83 

Decarbonized  surface 23-28-35-45-61-64 

3*3 


Deep  case  hardening 232 

Deep  fire  best 35 

Defects  in  steel — lack  of 302 

Degrees  of  hardness 284 

Depth  of  hardening 89 

Detecting  time  of  cracking 100 

Device  for  cooling  thin  plates 179-180 

Die  or  punch  hardest  ? 140 

Dies— baths  for  hardening 133-136 

Blanking  press .• 289 

Boxes  for  heating 132-224 

Cracking  from  internal  strains 154 

Drawing 290 

Drawing  temper  of 139 

Drop  forging 290 

For  cartridges  and  other  work 197 

Forming 144 

For  punching 241 

Furnace  for 130-131-137 

Heating  in  charred  leather 132 

Hardening 149-204-215-221 

Heating 40 

Heating  box  for 145 

Hobs  for 291 

Method  of  cooling 151 

Methods  of  hardening  129 

"Spring" 153 

Starting  scale  before  hardening 134 

Tempering 153 

Tongs  or  grappling  hooks 135-136 

To  prevent  cracking 138-139 

Punch  press  work 138-143-249 

Ring 144 

Ring — furnace  for 145 

Screw  cutting 289 

Swaging 289 

Threading  bolts 289 

Difference  in  steel 16 

Different  results  in  case  hardening 237 

Steels 26 

Difficult  pieces  to  harden 217-218 

Dipping  thin  pieces 245 

3H 


Dirty  water  for  cooling 95 

Disc  cracked  in  grinding 306 

Dont's 280-301 

Doubts  about  steel 274 

Drawing  dies 290 

Forming  dies 144 

Milling  cutters 167-168 

Punches 142-143 

Ring  dies 147-148 

Slitting  saws 183 

Springs 265-266 

Temper 56-116 

Temper  of  dies 139 

Temper  of  T  slot  cutters 174 

Draw  knives 228 

Drill  rod  not  good  for  punches 142 

Drills  for  rock 290 

Twist 290-309 

Prop  forging  dies 290 

Dull  cutters  spring  work 303 

Eccentric  centering 24 

Holes  in  articles 198 

Economy  in  heating 45 

Of  inspection, 33 

Effect  of  continued  heating 84 

Heat  on  hammered  steel 69 

Oil  on  temper  color 125 

Slight  changes  in  heat 123-124 

Emergency  annealing 74 

Emery  wheel— use  proper 307 

Equalizing  heat  of  lead  bath 106 

Error — common 279 

Even  heating  by  lead  bath 92 

Exact  tempering  by  thermometer 123 

Examples  of  hardening 127 

Expansion  and  contraction , 12 

Expended  bone  for  Bessemer  steel 233 

In  annealing 83 

Experience 16 

Experiment  in  partial  hardening 248 

Extravagant  economy 24 

Extreme  hardness 285 

3*5 


Falling  heat 62 

Files 290 

Method  of  hardening 99 

Fillets  in  counterbores 187 

T  slot  cutters 172-173 

Filling  corners  with  graphite  or  clay 176 

Fire-clay  to  prevent  hardening 249-250 

Fire  cracks 299 

Fixture  for  handling  ring  dies 147 

Fixtures  for  use  in  hardening 201-202 

Flashing  springs 265 

Flat  plates— methods  of  cooling 179 

Springs 270 

Flexibility  of  hardened  steel 66 

Fluxes 310-311-313 

Forging   68 

And  tempering  at  once 71 

Dies  (drop  forging) 290 

.  Improper 300 

Self-hardening  steels 279-280 

Troubles 68 

Forming  dies 144 

Tools 221 

Fuels 36-37-38 

For  hardening  baths 96 

Fumes  from  cyanide  furnace 52-53 

Lead  baths 47-51 

Furnace  for  case  hardening 242 

Case  hardening 253-254 

Dies 130-131-137 

Heating  baths 47-49-51-52 

Heating  springs 262 

Heating  taps 159 

Heavy  dies 136-137 

Lead  heating 96 

Pack  hardening 210 

Ring  dies 145 

Furnaces — location  of 54 

Gas  as  fuel 37 

Blast  for  heating 42-43-44-45 

Furnace  for  dies 137 

316 


Gas  pipe  for  case  hardening 228 

Gauges — aging  of 196 

Crack  from  grinding 305 

Hardening  ring 195-196 

Packing  for  hardening 240 

Snap  and  ring 215-216-218 

Gear  for  chainless  bicycles 235 

Genesis  of  pack  hardening 203 

German  steel 276 

Glass  bath  for  hair  springs 267 

Cutters 288 

Hardening  bath  for  watch  springs 54 

Heating  baths 46 

Government  method  of  hardening  files 98-99 

Grain  of  tool  steel 55-56-57-61 

Granulated  raw  bone 243 

Graphite  for  filling  corners 1 76 

Grinding  cracks  tools 305-306 

Taps  to  show  color 161 

Tools  right 307 

Gripping  jaws 292 

Grooved  rolls— hardening 192 

Gun  barrels 287 

Gun  frames — coloring 109 

Hardening 252 

Springs — cooling 182 

Hair  springs 267 

Half  round  reamers 162-163 

Hammer — blacksmiths' 290 

Machinists' 291 

Refining 69-70 

Hammered  steel 69 

Handle-bar  binders   235 

Handling  heavy  dies 135-136 

Maximum  amount  of  work 104 

Ring  dies 146 

Harden  at  lowest  heat 126 

Hardened  work — straightening 1 15 

Hardening 22 

Arbors 189 

A  screw  driver 184 

327 


Hardening  baths 85-86-S7-96-105 

Bessemer  steel 1 1 1 

Between  plates 178 

Bicycle  parts 235 

Compounds 88 

Cutting  tools 86 

Depth  of 89 

Dies 129 

Dies  without  "  twist  " 150 

Eccentric  pieces 198 

Files 98-99 

Fixtures 201-202 

Grooved  rolls 192 

Half  round  reamers 163 

High  carbon  steel 285 

Holes 90-93 

Hollow  mills 175 

Hot  water 1 13 

In  baskets 1 1 1 

Large  pieces 35 

Lead 96 

Locally 252 

Long  tools , 30-104-154-155-258 

Machine  for  thin  articles 180 

Machinery  steel 1 10-1 1 1-225 

Malleable  iron 110 

Mandrels,  arbors,  etc 189 

Milling  cutters 164-165 

Places 243 

Ring  dies 144-145-147 

Saws 178 

Screw  cutting  dies 149 

Shank  mills 169-170 

Small  tools—  mixture  for 98 

Springs 259-260-26 1-262-263-264-265 

Steel 112 

Taps  and  dies 53-156-160-202 

Temperature  of  different  steels 59 

The  punch 141 

Thin  pieces 178-244 

Walls  of  holes 195 

Watch  springs 54 

328 


Hardening  wood-working  tools 200-201 

Hardies  for  blacksmiths 29 1 

Hard  metals— steel  for 277 

Hardness— degrees  of 284 

Due  to  cyanide  bath 51 

Extreme 285 

Heat  depends  on  carbon 55 

For  welding '. 310 

High 297 

Necessary  to  draw  temper 117 

Of  lead  bath— care  about 102 

Rapid 298 

Refining 13-56 

Should  be  low  as  possible 13 

Slow 299 

Slowly  for  tempering 140-125 

"Soaking" 299 

Strength  depends  on 107 

Uneven 297 

Work — timing 231 

Heated  baths 66-92 

Advantages  of 156 

Heath 277 

Heating  articles  of  irregular  shape 67 

At  right  speed 60-61 

Box  for  ring  dies 145 

Cyanide  in  an  open  forge  .  ^ 52 

Cyanide  of  potassium 46 

Dies 40 

Dies  in  boxes 132 

Dies — proper  method 133 

For  hardening  with  lead  bath 96-100 

Gas  blast 42-43-44-45 

Glass 46 

Grooved  rolls 192 

In  a  forge 35 

Lead 46-49 

Tin 46 

Tubes  in  open  fire 63 

Large  work 45 

Long  tools  in  lead  bath 104 

Machine  for  slender  punches 143 

329 


Heating  mandrels 186-189 

Screw  dies  in  boxes 152 

Slender  punches 143 

Small  work  in  tubes 41-42 

Steel — methods  of 34 

The  baths 92 

To  avoid  strains 113 

Tool  steel 55 

Uniformly 14-60-62 

Various  substances 46 

Water  for  hardening  tools 104-1 13 

Wood-working  tools 201 

Work  in  cyanide  bath 105 

Heavy  and  light  portions 62 

Blows  when  hot 69 

Cuts 65 

Punches 142 

Springs 265 

High  carbon  steel 30-278-283 

Duty  steels 277 

For  punches 142 

Heats 297 

Heats  open  grain  69-70 

Speed  steel 277 

Hobs  for  dies 29 

Holes— hardening 90-93 

Hardening  out  of  round 195 

In  dies — cooling  of 93 

In  shank  mills 171 

Near  edge 198 

Stopped  with  clay 138 

Hollow  articles— to  prevent  cracking 175 

Danger  of  steam  forming  in 175 

Mills 174-175 

Home-made  furnace  for  dies 131 

Furnaces 39-40-47-49-53 

Gas  blast  oven 44 

Lead  heating  apparatus 49-50" 

Hot  lead  for  hardening 96 

Water  bath  for  springs 265 

Work— chisels  for 287 

How  to  case  harden  small  quantities 226 

330 


How  to  pack  harden 207 

Huntsman,  Benjamin 276 

Hydrocarbonated  bone 233 

Identifying  steel 33 

Imitation  case  hardening Ill 

Importance  of  cutting  point 7 

Improper  forging 300 

Heating  and  hammering 70 

Impure  lead  injures  steel 97 

Increase  in  production 10 

Indifference  of  some  hardeners 64 

Inspection  of  steel — economy  of 33 

Internal  strains 65-79 

Strains  in  dies 154 

Iron  boxes  for  annealing 75-76-77 

Irregular  shaped  work 62-67 

Jaws  for  bench  vises 291 

Chucks 291 

Cutting  pliers 291 

Gripping 292 

Pipe  machines 292 

Screw  threading  dies 292 

Wire  pullers 292 

Jarolinech 13-59 

Kettle  for  tempering  in  oil 122 

Key  ways 307 

Knife  blades 292 

Knives — draw  knives 292 

Knowing  it  all 16 

Labeling  steel 33 

Lack  of  ability 129 

Large  baths 95 

Fire  best  for  hardening 190 

Tanks  best 139 

Work—  caution  about 222 

Lathe  centers 287 

Tools 292-^09 

Tools — tempering 120 

Lead  and  crucibles 97 

Bath  for  hardening 96 

331 


Lead  bath  sometimes  unsatisfactory — why 97-102 

Furnace — handling  work  in 104 

Hardening  furnace 47-48 

Heating  baths 46-49 

Heating  furnace 96 

Should  be  pure 97 

Sticking  to  work 98-102 

Too  hot — caution  about 102 

Leather — charring 313 

Charred  for  annealing -. 85 

For  heating  dies 132 

Length  of  time  to  heat 23 1 

Liability  of  cracking 271 

Lighter  blows  when  cooling 69 

Lime  for  annealing 72 

Local  case  hardening 249-250 

Hardening 252 

Location  of  furnaces 54 

Locomotive  springs 296 

Long  taps — best  methods  for 158 

Tools— hardening 154-155 

Loss  due  to  poor  hardening 9-10 

Low  carbon  steel  for  tools 272-274 

Heats  best 13 

Heats  for  tempering 124 

Lowest  heat  best  for  hardening 126 

Lubricating  tools 309 

Machine  for  hardening  thin  articles 180 

Steel  for  tools 241-271-274 

Taps '. 296 

Machinery  crucible  steel 293 

Case  hardening 225 

Hardening Ill 

Steel 19 

Machinists'  hammer 291 

Makeshift  oven •  128 

Making  a  screw-driver 184 

Malleable  iron — hardening 1 10-1 1 1 

Mandrels 293 

And  arbors 219-220 

Taper 186-189 

33^ 


Men  who  harden 15 

Mercury  bath 85 

Metcalf  on  "  refining  heat " 56 

Method  of  cooling  gun  springs 182 

Cooling  for  hardening 89-90-91 

Drawing  temper 118 

Heating  steel 34 

Milling  cutters 55-204-2 12-213-288-307-309 

Arbors 286 

Drawing  temper  of 167 

Hardening 164-165 

Machine 286 

Reamers  or  taps 304 

Mixing  of  different  grades 28 

Mixture  for  color  work 233 

Hardening  small  tools 98 

Hardening  springs 260-26 1 

Heating  wood-working  tools 201 

Machine  steel  tools 240-243 

Mould  for  casting  lead 101 

Mowers 293 

Muffle  furnace  for  heating  taps 159 

Furnaces 37-4 1 

Mushet 277 

Mysteries — absence  of 25 

Nature  of  steel 1 1-80 

Neat's-foot  oil 261 

New  charcoal  best 36 

Nickel-plating  prevents  case  hardening 251 

Non-crackers 11 

Nuts — case  hardening 251 

Oil  affects  temper  color 125 

And  water  bath 88-167 

Bath 86 

For  case  hardened  work 234 

Hardening 211-212-214 

Hardening  thin  articles 181 

Kettle 122 

Long  tools 104 

Removing  strains 67-68 

333 


Oil  for  hardening  springs 263-264 

Tempering  furnace 121 

Toughens  springs 259 

Wood-working  tools 200-201 

Overheated  steel — restoring 298 

Overheating 13 

In  annealing 74-75-83 

Oxidized  steel 63 

Pack  hardening 203 

Arbors  and  mandrels 219-220 

A  "teaser" 218 

Bath  of  oil  for 21 1-212 

Bicycle  parts 236 

Blanking  dies 214 

Boxes  for 206 

Danger  in  cast  iron 206 

Depth  of  hardened  surface 205 

Dies  and  taps 215-221 

Difficult  pieces 217 

Don't  use  bone 205 

Forming  tools 22 1 

Furnace  for 210 

Gauges 215-216-218 

Heat  of  boxes 210 

How  to  do  it 207 

Large  work 222 

Long  articles 209 

Mandrels  and  arbors 219-220 

Method  of  packing 206 

Milling  cutters 212-213 

Phosphorus  to  be  avoided 205 

Possibilities  of 224 

Reamers 222-223 

Similar  articles  together 208 

Swaging  dies 223 

Tanks  should  be  convenient 222 

Taps  and  dies 215-221 

Time  necessary 211 

Wiring  the  work 207 

Wrong  way  of  doing 208 

Packing  for  case  hardening 228 

334 


Packing  gauges  for  hardening 240 

Material 232 

Pan  of  sand  for  drawing  temper 118 

Partial  heating 127 

Paste  for  coating  small  tools  98 

Covering  work 46 

Peculiarities  of  tool  steel 22 

Percentage  of  carbon 15-20-21-29-33 

Carbons  for  tools 284 

Penetration  of  carbon  in  iron 275 

Phosphorus  affects  steel 272-283 

Bad  effects  of .' 83 

Makes  steel  brittle 252 

Piercing  punch 141 

Pinion  gear — hardening  of    237 

Pipe  cutters 288 

Machine  jaws 292 

Pipes  in  steel  bars 32 

Planer  tools 293-294 

Plates — cooling 179 

Pliability  of  hardened  steel 66 

Pliers  for  cutting 29 1 

"  Points"  of  carbon 21 

Poisonous  fumes 47-52-53 

Potash 261 

Preventing  decarbonization  locally 46 

Dross  forming  on  top 101 

Lead  sticking  to  work 98-103 

Local  hardening 249-250 

Springs  in  ring  gauges 195 

Prevention  of  cracking 138-139 

Springing  of  long  articles 30 

Process  of  annealing  in  boxes 77 

Production — cheapening  cost  of 8 

Increase  in 10 

Prussiate  of  potash  for  case  hardening 226 

Punch — buckling  of 141 

Blacksmiths 294 

Blanking  work 294 

Drawing  temper  of 142-143 

Hardening  of 141 

Heating  machine  for 143 

335 


Punch  for  hot  trimming 294 

Sheet  steel 141 

Track  work 295 

Punch  or  die  hardest  ? 140 

Punch  press  dies 133-143-241-289 

Quality  and  carbon 22 

Quantity  of  work  to  be  case  hardened 226 

Rapid  heating 60-61-298 

Raw  bone  contains  phosphorus 252 

Razor  temper 20 

Reamer — heating  a  long 128 

Reamers 158-162-222-223-295 

Dull  cutters  may  spoil 303-304 

Half  round 162-163 

Heating  in  lead  -bath 104 

Reasons  for  temper  colors 124-125 

Using  lead  bath 100 

Reducing  worn  dies 197 

Refining— heat 13-56-60 

By  hammering 69-70 

Temperature 13-56-60 

Reheating  to  draw  temper 116 

Remove  strains 65-66-67 

Reliable  steel 282 

Removing  lead  from  steel 102 

Strains  from  grooved  rolls 194 

Rendered  beef  suet 261 

Resin 261 

Use  of— caution 104-105 

Restoring  burnt  steel 298 

Results  of  case  hardening 237 

Revolving  furnace  for  drawing  temper 1 18-1 19 

Ring  dies 144 

Drawing  temper 147-148 

Furnace  for 145 

Hardening 144-145-147 

Ring  gauges — hardening  of 195-196 

Rings  without  welds 311-312 

Rising  heat 62 

Rock  drills 290 

336 


Rotting  of  steel 88 

Roughing  out  work 24-25 

Safety  valve  springs 269 

Sal  ammoniac  for  case  hardening 226 

Salt  and  cyanide  bath 53-105 

Salt  for  case  hardening 226 

Satisfactory  annealing 75-76 

Saturated  solution 86 

Saw  arbors 236 

Saw-file  temper 21 

Saws  for  wood 295 

Hardening  of 179 

Steel 295 

Tempering 183 

Scale  formed  in  dies— removing 134 

Scrapers 295 

Screw  cutting  dies 289 

Hardening 149 

Method  of  heating 152 

Preventing  twist 150 

Screw-drivers 183-186-295 

Screws— case  hardening 238 

Screw  threading  dies 148-229 

Seasoning  of  gauges 196 

"  Second  blue  " 268 

Self-hardening  steel 278 

Annealing 28 1 

Separating  steel ... 33 

Set  temper 21 

Shafts  for  high  speed 295 

Shank  mill — cooling 94 

Shank  mills— hardening 169-170 

Methods  of  making 170 

With  holes 171 

Shapes  of  steel  bars 28 

Sharp  corners  to  be  avoided 178 

Shear  steel 276 

Sheet  steel — annealing 270 

Springs 270 

Shifting  the  blame 80 

Singing  of  steel  in  bath 90 

337 


Slender  articles — hardening 258 

Slender  tools 273 

Slitting  saws— drawing  temper 183 

Slotting  saws — hardening  of 176 

Slow  heating..  ..    60-61-299 

Best  for  tempering 125 

Small  bath  for  cooling 94-95 

Lots  of  case  hardening 226 

Pieces—  method  of  case  hardening 229 

Taps,  reamers,  etc 158 

Work — heating  in  tubes 41-42 

Snap  gauges 215-216-240 

"Soaking" 299 

Soft  places  on  work 249-250 

Portions— leaving 248 

Soap 261 

Spots  where  lead  sticks  to  steel 102 

Special  preparations 232 

Steels 275 

Spermaceti  oil 261 

Sperm  oil  for  springs 26 1 

Spindles 242 

Spindle  steel 295 

Temper 21 

Spirit  lamp  for  heating 44-45 

Spoiled  steel 9 

Spring  dies 152 

Springing  of  mandrel 304 

To  prevent 155 

Spring  of  work  by  dull  cutters 303 

Springs— bath  for 86-260-261 

Best  steel  for 259 

Carriage 296 

Clocks 260 

Colors  of 269 

Danger  of  bending  cold 269 

Flat  stock 270 

Furnace  for  heating 262 

Locomotive 296 

Safety  valves 269 

Sheet  steel 270 

Method  of  cooling 262 

338 


Springs — toughened  by  oil 259 

Tempering 259 

Watches 54-267 

Stamps  for  steel 295 

Steam  forming  in  hollow  articles 175 

Prevents  cooling 93 

Steel 19 

Affected  by  phosphorus 272 

Air  hardening 278 

Alloy 277 

Bessemer 286 

Better  than  ever 277 

Blister 276 

Cast 286 

Cemented 275 

Choice  of 28 

Converted 275-286 

Crucible 279-286 

Difference  in 16 

Different 26 

Doubts  about 274 

For  chilled  iron 281-282 

For  hard  metals 277 

For  mandrels  or  arbors 189 

For  slender  tools 273 

For  various  tools 282-285 

German 276 

Hammer  refined 70 

(Machine)— tools 271-274 

Machinery 20 

Nature  of 11 

None  best  for  all  purposes 30 

Open  hearth 286 

Pliability  of 66 

Saws 295 

Self-hardening 278 

Shear 276 

Spoiled 9 

Stamps 295 

Usually  all  right 27 

Tool 20 

To  use  for  springs 259 

339 


Steels — special  275 

Stiffness — how  to  secure 252 

Stirring  lead  bath  to  equalize  heat 102-104 

Stock — keeping  separate 28 

Stone  work 288 

Chisels  for 288 

Working  tools 293 

Stop  all  holes  in  dies  with  clay  138 

Straightening  hardened  work 115 

Steel 66-301 

Work 26-30 

Work  that  is  sprung 79 

Strains  in  grooved  rolls 194 

Internal 65-79 

Internal — in  dies 154 

Removed  by  reheating 65-66-67 

Strength  depends  on  heat  used 59-64 

Study  of  steel 11-18-80 

Substitute  for  borax 313 

Successful  steel  working ^ 18 

Sudden  heating  is  dangerous 140 

Sulphur  in  lead — avoid  it 97 

Surface  carbon  63 

Square  corners  in  counterbores 187 

Supporting  cutting  edges 308 

Swaging  dies 223-289 

Heating  boxes  for 224 

Sweeps  for  moving  pieces  of  work 258 

Tallow  for  tempering  springs 265 

Tank  for  hardening  small  work 230 

Reheating 66-67 

Tanks  for  case  hardening 255-256 

Should  be  convenient 222 

Should  be  large 139 

Taps 296 

Brightening  for  color 161 

Furnace  for  heating 159 

Hardening 156-160-204-215-214 

Hardening  bath  for 157-158-160 

Machine 296 

Taper  mandrels 186 

340 


Temper 20-21-28 

Chisel 21 

Milling  cutters 213 

Razor  20 

Saw  file 21 

Set 21 

Spindle 21 

Tool 21 

Tempers  of  tools 283-284 

Temperature — critical  13 

Colors 123-125 

For  drawing  small  dies 153 

Grades  of 20-21 

Of  counterbores 188 

Of  lead  for  hardening 103 

Refining 13-56 

Tempering 116 

A  screw  driver 164 

At  very  low  heats 124 

Heat  necessary ' 117 

In  a  revolving  furnace 1 18-1 19 

In  oil 121 

Is  softening 1 16-126 

Lathe  tools 120 

Milling  cutters 167-168. 

Ring  dies 147-148- 

Saws 18a- 

Small  dies 153- 

Spoiled  steel 82: 

Springs 259-265-266. 

Springs  by  thermometer 266 

Taps 162 

To  "second  blue" 268 

Temporary  bath  for  hardening 257 

Furnace  for  oil 121 

Tepid  water  for  hardening 176 

Test  after  hardening 30  j 

Pieces 57-58-61 

Wires  in  annealing 76-77 

Wires  when  case  hardening 227 

Testing  a  screw  driver 185 

Bars  in  stock 32 

341 


Testing  bicycle  crank 82 

Hardened  work 82 

Heat  of  boxes 210-212 

Steel 33-57-58-61 

Work  occasionally 244 

Thermometer — care  of 266 

For  gauging  heat 1 19-21 1 

In  spring  tempering 266 

Thin  articles— hardening 180-244 

Threading  dies 148-289-292 

Time  for  heating  gauges 240 

Needed  for  pack  hardening 211 

Timing  heat  of  work 23 1 

Tin  heating  baths 46 

Tool  steel 20 

Heating  of 55 

Temper 21 

Tools  cut  faster  if  pack  hardened 204 

For  chilled  iron 283 

Hard  work 33 

Importance  of  cutting  point 7 

Lathes  and  planers 292-293-294 

Of  machine  steel 241-243-271-274 

Steel  for 282-285 

Stone 293 

Weakened  by  grinding 308 

Wood-working 293 

Tongs  for  hardening  mandrels  or  arbors .191 

Hardening  thin  articles 178 

Heavy  dies 136 

Preventing  hardening 249-250 

Toughening  bath 87 

Steel  239 

Toughness — how  to  produce 252 

In  wood-working  tools 200 

Tubes  for  heating  small  work 41-42 

Turpentine 261 

Track  work  punches 295 

Trimming  punches 294 

Trouble — causes  of 297 

Troubles  from  forging 68 

T  slot  cutters 171-172-173-174 

34^ 


Twist  drills 290 

In  hardening  dies 150 

Types  of  furnaces 37-38 

Hollow  mills 177 

Uneven  hardening  from  small  baths 255 

Heating 14-26-60 

Heats 297-302 

Uniform  annealing  heat  necessary 84 

Heating 14-26-60 

Heats  the  secret  of  success 1 12 

Temperature  necessary 264 

Valuable  men  to  have     128 

Vent  holes  in  hollow  mills 176-177 

Vine-like  effect  in  coloring 109 

Warm  water  for  hardening 176 

Waste  through  improper  handling 9 

Watch  spring  hardening 54-267 

Water  annealing 73 

Bath 86 

Cooled  oil  bath 214 

May  crack  work 306 

Welding 310 

Heat  for 310 

Rings — how  to  avoid 31 1-312 

Steel— don't 311 

Wine  suppers  and  steel 87 

Wire  pullers 292 

Wires  for  testing  heat 76-77 

Wiring  pieces  to  be  hardened 207 

Wood  saws 295 

Chisels 287 

Tools 199-200-201-293 

Working  augers 287 

Work  done  depends  largely  on  tools , 7 

Of  tool  depends  on  heat  used 126 

Workman 15 

Wrong  annealing 82 

To  anneal 81 

Way  of  pack  hardening 208 

Wrought  iron— case  hardening 225 

343 


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